Bulletin
OF THE

Illinois State Laboratory
OF

Natural History

Urbana, Illinois, U. S. A.

STEPHEN A. FORBES, Ph.D., LL. D.,

Director

Vol. IX. March, 1912 Article V.

THE VEGETATION OF THE BEACH AREA IN NORTHEASTERN
ILLINOIS AND SOUTHEASTERN WISCONSIN

BY

FRANK CALEB GATES, A.B.



ERRATA AND ADDENDA

Page 54, lines 3 and 2 from bottom, and elsewhere in Article III. for Cassia

chainaechrista read Cassia chamaccrista.

Page 62, between lines 4 and 5 from bottom of table insert Erigeron annuus.

Page loi, table, after Croloii glandulosus read var. septentrionalis: and for

Eijuisettim laeinyatum read Eqnisetum bycmale var. inlermedium.
Page 131. line 3, for coerulea read caerulca.

Page 138, last line, for Zi::a read Zizia.

Page 141, line 21 from bottom, dele Diodia teres.

Page l6g. between lines 3 and 4, insert as follows

:

Erigeron annuus (L.) Pers. An interstitial in the liunch-grass association

in the Hanover area.

Page 177, line 5, for casti^'ard read iveslzvard.

Page 209. line 3 from bottom, for copalina read copallina.

Page 210, line 13 from bottom, for Diospyrus read Diospyro'i.

Page 211, line 5, for Foresteria read Foresticra.

Page 256, line 3 of table, for Dr. H. M. Pepoon read H. 5". Pepoon.
Page 278, line 16, the fifth word should be in Roman type.

Page 286, line 6 (second column), page 295, list of secondary species (second
column), and page 353. line 8 from bottom, for hiematis or hiemale read hye-
mnte.

Page 313, line 4 from bottom (first column), for pedicularis read pcdicularia.

Page 315, line 10, second column, for Apoeynum read Apocynum.
Page 323, line 3 from bottom, for Cyperus read Scirpus.

Page 330, line 14, for virginianum read inrginicum.

Page 336. lines 3 and 2 from bottom, for virginicum read virginianum.
Page 337. line 2 from bottom, for philadelphicum read philadelphicns.

Page 339» in first list of invading species, for Rhus hiria read Rhus typhiua.

Page 351. line 4 from bottom, for .verophtic read .verophytic.

Page 355, above line 6 from bottom, insert Scirpus heterochaetus Chase.
Page 356, line 14 from bottom, for Symlocarpus read Symplocarpus.
Page 360, line 14, for Pirus read Pyrus.
Page 362, after line 7, insert Acer saccharinum L.

Page 363, line 2 from bottom, for quadiflorum read quadriflorum.
Page 365, line 14, for Ihapus read thapsus.
Page 369, last line, for Tanecelum read Tanaceium.
Page 417, line i. dele the.

Page 497, line 9 from bottom, for neglible read negligible, and in foot-note, for
Auslall read Anstalt.

Page 498, line 4 from bottom, for Lockport read Chillicothe.

Page 500, line 13 from bottom, after up insert in.

Page 5or, line 2 from bottom, for dissolving read dissolved.

Page 504, line 23, for gryina read gyrina : line 17, for dentata read knickerbockeri.
Page 506, line 11, for vernata read ternala.

Page 507, line 3 from bottom, for Macon read tt'asoi.

Page 513, line 19, for Nepa read Zaitha; line 18, and page 517, line 13 from bot-
tom, page 520, line 12 from bottom, and page 532, line 4, read naid or naids
for naiid or naiids.

Page 517, line 6 from bottom, for pondiveed read pickcrel-iveed.



Page 519. for first sentence of last paragraph read as follows:

We have no exactly comparable chemical data for July; but analyses

for August give percentages of saturation for Morris and Marseilles as follows :

20.4 per cent, at Morris on the nth and 11 per cent, at Marseilles on the 12th;

16.35 P<^r cent, at Morris on the 22d and 23d and 7.4 per cent, at Marseilles on
the 24th and 25th.

Page 521, line 6 from bottom, and page 529, line g, for chrysoleucas read cryso-

leticas.

Page 525, line 22, and page 536, lines 21 and 24, for Ekmann read Ekmnn.
Page 532, line i, for Ancyclus read Ancylus.
Page 551, line 7, for 00 read 572.

Page 615, second line above foot-note, for 106 read 94.

Page 616, line I, for the second Biindeln read Bilndel; line 2, for Biindeln read
Biindcls; line 3, for ausscrn read ausscren; line 6, for sweierlie read sweierlei.

Page 629, line 12, for kciii read kcincn.
Page 634, line 9, for untcrnommcn read untcninntincnen; and in line 14 from

bottom, after ;;/$ insert is fig.

Plate III, Fig. i, after the word mixed in legend insert consocies of the.

Plate IX, Fig. 2, dele the legend and read instead ; Root-system of Tephrosia
virgiiiiana, exposed by blowing of the sand.

Plate X, Fig. 2, dele the legend and read instead ; A blowout almost stabilized

by bunch-grasses, especially Leptoloma cognatum.
Plate XXXIX. for Calainogrostis read Calamagrostis.
Plate LIV. exchange places of cuts, but not the legends.
Plate LXXXV, for 7 read ye.



CONTENTS

PAGE

Introduction 255

Location and Physiography 256

Physiographical History 257

Climate 259

Edaphic Factors 259

Influence of Lake Michigan 260

General Description of the Area 261

Associations : General Consideration 262

The Lower and Middle Beach Associations 266

The Chlaviydoinonas Association 266

The Cakile-Xanfhinin Association 260

The Middle Beach Pool Associations 273

The Juncus alpinns insignis Association 273

The Triglochin palustris Association 274

The Carex oederi pumila-Cyperus rivularis Association 274

The Sabatia-Linum Association 275

The Juncus balticus littoralis Association 276

The PotentUla anserina Association 278

The Dune Formation 280

The Dune Associations 282

The CalainovUfa longifolia Dune Association 282

The Ammophila arenaria Dune Association 283

The Salix syrticola Dune Association 285

The Prunus pumila Dune Association 286

The Popxdus candicans Dune Association 287

The Elymus canadensis Dune Association 287

The Juiiiperus Dunes Association 288

Miscellaneous Dunes 289

The Populus-Sali.v Dune Association 289

The SalLv glaucophylla Dune Association 290

The Panicum znrgatum Dune Association 290

The Andropogon scoparius Dvtne Association 291

The Popiilus-Salix-Cornus Thicket Dune Association '. 291

The Betula alba papyrifcra Dune Association 291

The Relic Dune 292

The Man-made Dune 292

The Traveling Dune 293

The Upper Beach Associations

:

The Artcmisia-Panicum Association 293



The Bunch-grass Association : pack

The Aiidro[logon scoparius Consocies 295

Tht Sporobolus heterolepis-Sorghastruui nutans Consocies 300

The Liatris scariosa Association 30 r

The Poa coinpressa Association 303

The Arctostaphylos-Jimiperus Heath Association 306

The Pine Forest Association 308

The Qtiercus veUttina Association 311

The Blowout Associations 315

The Associations of the Marsh Habitats 318

The Plankton Association 319

The Chara Association 319

The Potamogeton Association 319

The Castalia-A'ymphaea Association 320

The Ranunculus aquatUis capillaceus Association 321

The Lentna-Riccia Association 322

The Mcnyanthcs-Sagittaria Association 322

The Carex Association 324

The Phragmitcs-Typha Association 326

The Scirpus ralidus Association 327

The Scirpus ainericanus Association 328

The Cladium mariscoides Association 329

The Calamagrostis canadensis Association 330

The Iris versicolor Association 332

The Osmunda Association ZiZ

The Potentilla fruticosa Association 334

The Liatris spicata Prairie Association 335

The Juucus torreyi Association 340

The Thicket Associations

:

The Populus-Salix-Cornus Thicket Association 340

The Prunus Thicket Association 342

Transects of the Associations 344

General Conclusions 348

Summary 35 f

List of the Species of Plants growing on the Beach Area 353

Bibliography of the more Important Works Consulted 370



LIST OF ILLUSTRATIONS

General map of the southern part of the Beach area Plate XXXVII
General map of the northern part of the Beach area Plate XXXVIII
Diagram showing the successions exhibited between the

plant associations of the Beach area Plate XXXIX
Wind direction; sunshine and temperature curves Plate XL
Diagrams showing precipitation Plate XLI
Diagram showing snowfall Plate XLII
Fluctuations of Lake Michigan, 1854-1908 Plate XLIII

An oak ridge near Kenosha, Wisconsin Plate XLIV, Fig. i

A beach pool near Waukegan, Illinois Plate XLIV, Fig. 2

Little dunes of Euphorbia polygonifolia Plate XLV, Fig. i

Diagrams illustrating the character of the shore south of

Kenosha, Wisconsin Plate XLV, Fig. 2

Relic dunes south of Kenosha Plate XLVI, Fig. i

A Juncus balticus littoralis relic dune Plate XLVI, Fig. 2

A relic dune partly destroyed by freezing water Plate XLVII, Fig. I

A Calanwvilfa dune Plate XLVII, Fig. 2

The bluflf at Camp Logan, Illinois Plate XLVIII, Fig. i

Aminophila, Salix glaucophylla, and Populus candicans dunes. Plate XLVIII, Fig. 2

Section of a Juniperus dune Plate XLIX, Fig. i

Salix glaucophylla dune in winter Plate XLIX, Fig. 2

Growth habit of Sporobolus cryptandrus Plate L, Fig. i

Andropogon scoparius bunch-grass prairie Plate L, Fig. 2

Growth habit of Petalostcmum purpureum f. arcnaritim Plate LI, Fig. I

Blowout in Quercus vcluiina association Plate LI, Fig. 2

The heath at Beach, Illinois Plate LII, Fig. i

Blowout in the heath association Plate LII, Fig. 2

Blowout in the edge of the Quercus velutina association Plate LIII, Fig. i

Marsh associations in the Dead River, near Beach, Illinois. ...Plate LIII, Fig. 2

Scirpus atnericanus and Scirpus z'alidus associations Plate LIV, Fig. i

Swale showing the Cladium association Plate LIV, Fig. 2

Swale and ridge, showing Calamagrostis and aspens and

willows Plate LV, Fig. i

Prairie showing the Phlox glaberrima aspect Plate LV, Fig. 2

Prairie showing Liatris spicata Plate LVI, Fig. i

The invasion of the prairie into the pines Plate LVI, Fig. 2

%l



Article V.

—

The Vegetation of the Beach Area in Northeastern

Illinois and Soiith.eastcrn JVisconsin. By Frank Caleb Gates.*

Introduction

During the university year of 1909-1910 at the University of Illi-

nois, the results of the two previous summers' work on the area be-

tween Waukegan, Illinois, and Kenosha, Wiconsin, were presented in

a bachelor's thesis, entitled "The Plant Associations of the Recent

and Fossil Beaches of Lake Michigan between Kenosha, Wisconsin,

and Waukegan, Illinois." The first half of the present article is taken

bodily from that thesis, with whatsoever additions and omissions

seemed most advisable.

The original article was written under the immediate super\-ision

of Dr. H. A. Gleason, now of the University of Michigan. To him
I am under the greatest obligations for innumerable suggestions both

in interpreting the data and in putting them in written form. To Dr.

H. S. Pepoon, of the Lake View High School, Chicago, to Dr. C. C.

Adams, of the University of Illinois, and to Prof. L. M. L^mbach, of

Northwestern College, Naperville, Illinois, I am indebted for sug-

gestions and other helpful features. The data for plotting the cli-

matic factors were obtained through the courtesy of the Chicago and

Milwaukee offices of the United States Weather Bureau ; and the

data for the levels of Lake Michigan, from the City Engineer's office,

in Chicago.

The nomenclature used, is that of the seventh edition of Gray's

Manual, since that is the latest taxonomic work.

The region under consideration is located near the northern limit

of the type of vegetation known as the Deciduous Forest Provincef

and not very far from the eastern limit of an arm of the Prairie Prov-

ince.* At the same time it is near the southern limit of the North-

eastern Conifer Province? and has within its area associations that

are relics of that province.

*Submitted with spelling in accordance with the rules and recommendations of the

Simplitied Spelling Board.

tDeciduous Dicotylous Forest. Warming, 1909:329 ct sc(|. Deciduous Forest

Province. Gle.\son, 1910:43.

tPrairie Province. Pound and Clements. 1898. Grass-steppe (Prairie).

Warming, 1909:285-86. Prairie Province. Gleason, 1910:43.

§Evergreen Coniferous Forest. Warming, 1909:315. Northeastern Conifer

Province. Gleason, 1910:43.



256

The aim of the work was to obtain a clear idea of the extent and
floristic composition of the associations of the region to serve as a

foundation for further work upon the successional relationships be-

tween the competing associations of the three provinces which are

represented in the area.

Although the region had been visited for collecting purposes dur-

ing some of the four years previous to 1908, work upon a strictly

ecological basis was pursued only during the seasons of 1908, 1909,
and 1910. A summary of the trips taken is here presented in tabu-

lar form.



257

County, Wisconsin, lying between 42° 21' and 42° 35' nortli latitude

and between 87° 48' and 87° 49' west longitude. The western bound-
ary of the region under consideration, is the Glenwood ridge, which
was the upper limit of glacial Lake Chicago, a brief discussion of

which will presently follow. The region is entirely covered by the

Racine (Wisconsin) and the Waukegan (Illinois-Wisconsin) quad-
rangles of the United States Geological Survey. The latter is by far

the more detailed sheet and covers the greater part of the area. Parts

of these two sheets have been used directly in making up Plates

XXXVII and XXXVIII. Differences in elevation are very slight.

The highest elevation on the Beach region proper is but nine meters,

while virtually all of the area, with the exception of a few of the

ridges, is less than five meters above the level of Lake Michigan.
The Glenwood ridge, which forms the western boundary, is about

seventeen meters above the Lake Michigan level.

Geologically the region consists of a sand and gravel beach super-

imposed upon glacial clay. In but one place, so far as was discov-

ered, is the clay exposed. The sand is arranged in long ridges not

quite parallel to the present shore-line. Between the ridges are

swales, only a few of which are able to drain directly into Lake Michi-

gan. Drainage is largely accomplished by seepage of the water
through the sand and finally into the lake. In the vicinity of Wau-
kegan, as indicated on the map (PI. XXXVII), are two bodies of

water located at practically lake level. These drain into the lake only

during periods of rather heavy rainfall and during the spring thaws.

Physiographical History

The western boundary (Glenwood ridge) of the region under

consideration was formed by Lake Chicago, the body of water that

occupied the southern end of the Lake Michigan basin during the re-

treat of the Late Wisconsin Glacier. This glacial lake had a south-

western outlet into the Illinois River. By erosion of the outlet the

lake level was reduced to 16.8 meters (55 ft.) above the present Lake
Michigan. The process known as "stopping" caused a rather sudden

transition from the Glenwood level to the Calumet level, which was
about 10.6 meters (35 ft.) above the present one. During this period

the ice-sheet retreated into the north until a low pass to the northeast

was uncovered, which caused a lowering of the lake below tlie pres-

ent level. A re-advance of the ice-sheet raised the water to approxi-

mately the 7.6 meter level which is known as the Tolleston stage. At
this time Lake Maumee, which occupied the upper Erie and lower

Huron basins, emptied into Lake Chicago through the Grand River,



258

which flowed across the present state of Michigan. Withdrawal of

the ice-sheet uncovered an opening in the Mohawk Valley through

which was drained Lake Warren, formed by the coalescing of the

lakes in the Huron, Erie, Ontario, and Saginaw basins. Contempo-

raneous with this new outlet was the abandonment of the Grand

River outlet into Lake Chicago. As the ice withdrew further, the

lakes in the Michigan and Huron basins coalesced through the Straits

of Mackinac, and the dismemberment of Lake Warren followed.

With the uncovering of the Superior basin the lakes of that region

together with those of the Michigan and Huron basins formed Lake
Algonquin, which at first had a discharge through Port Huron and,

at times of high water, through the Chicago outlet also. It seems

possible that there may have been, in addition, an outlet to Lake Iro-

quois through the Trent Valley in Ontario. The land in the north-

east began to rise when relieved of the weight of the glacier, and

both Chicago and Port Huron outlets were in use until the Port Hu-
ron outlet was lowered, when this received all the drainage.

The next step was the opening of a pass near North Bay, Ontario,

which resulted in what are tenned the Nipissing Great Lakes. These

were at a low stage and discharged through the northeastern outlet.

Warping of the land there, however, finally brought the water up to

the Port Huron level, and when the land in the northeast continued

to rise the Port Huron outlet was resumed. From that time to the

present, such changes in level as have occurred, are due to the wid-

ening and deepening of the Port Huron channel and to the fluctua-

tions incident to variations in rainfall. Detailed accounts of the his-

tory of the lakes since the glacial epoch can be found in nearly any

work dealing with the geology or physiography of the LTpper Lakes

region. The three following have been consulted especially

:

GoLDTHWAiT, T. W. The Abandoned Shore-Lines of Eastern

Wisconsin." Wisconsin Geological and Natural History Sur-

vey, Bulletin 17:2-9. 1907.

GoLDTHWAiT, J. W. The Records of the Extinct Lakes. Illinois

State Geological Survey, Bulletin 7:54-68. 1908.

LeverETT, Frank. Outline of the History of the Great Lakes.

Twelfth Report of the Michigan Academy of Science, pp. 19-

42. 1910.

The Beach area itself consists merely of sand-bars which were

formed during the Tolleston stage, at which time the water was cut-

ting into the Calumet ridge. The sudden drop in level which ended

the Tolleston stage left these sand-bars emerged. Fonnerly diis ter-



259

race extended along the whole border of the lake, but with the ele-

vation of the water during the Nipissing stages the greater part of

the terrace was washed away except in the Chicago district and in

the area north of Waukegan. This interpretation, which signifies

that the ridges are of cdiout equal age, is substantiated by observa-

tions upon the plant associations. Jennings, in his work on Presque

Isle (1909: 294-305), under "historical development," says that the

ridges were formed at different dates, and that a line of plant suc-

cessions could be traced which confirmed the physiographic inter-

pretation. In the Beach area, however, evidence goes to show that,

with the exception of the fringing dune from Zion City down to

Waukegan, the ridges were formed at one time. The fringing dune,

as it now exists, is undoubtedly a product of historic times. Since

the building of the piers to protect the harbor at Waukegan, con-

siderable sand has accumulated north of it, and the formation of a

new dunal ridge a little north of the pest-house is now (1910) be-

ginning to show. North of Zion City, particularly between Win-
throp Harbor and Kenosha, the shore-line is being washed away a

noticeable distance every year. These ridges are all obliijue to the

present shore-line but they are parallel, or very nearly so, to the

shore-line that existed at the time of their formation, namely, the

Calumet ridge. The work of erosion, which bid fair to allow the

lake access to the Glenwood ridge south, as well as north, of Kenosha>
has been to a considerable degree, checked by piers at Kenosha and
by breakwaters, liehind which the lake is being artificially filled.

Clim.vte

As there are no weather bureau stations in the region having

records of long duration, the records of the stations at Milwaukee

and Chicago, situated at equal distances north and south of the area,

are used. It is fairly safe to assume that the records for this region

in very similar sort of country may be obtained by interpolating those

given. It is recognized that these data do not actually give the con-

ditions under which the plants live, but only a general indication of

the climate. The records are given in curves to facilitate in-

terpretation (PI. XL-XLII). As climatic factors do not usually

have edaphic influence, they are of value only in determining the gen-

eral character of the vegetation that will occupy a given area.

Edaphic Factors

Far more important than the climatic factors in determining the

floristic composition within an area are the edaphic factors. Of



260

these, the most important in itself is probably water. This region is

abundantly supplied with precipitation quite uniformly distributed

throughout the year. In addition, it lies in the immediate proximity
of the water-table level of Lake Michigan, which makes it to a large

degree independent of precipitation. The sandy soil is cjuite favor-

able for furnishing the plants with water, which the particles of

sand hold as capillary films. The physiological supply is probably
about 95 per cent, of the physical supply.

What seems the second factor in importance is the food material

in the soil. Sandy soil is notably deficient in soluble food material.

The relatively rapid eremacausis* characteristic of sandy soils,

caused by ready admission of atmospheric oxygen, accounts for the

destruction of much of what would have been available plant food

under other environmental conditions. Furthermore, soluble mate-

rials, and even insoluble ones, are gradually leached out of the soil as

the rain percolates through it instead of running off as it does in

most soils.

With respect to light, plants of the sandy soils thrive best with a

maximum, and this partially explains the lack of density in the vege-

tation under trees on the sand. Wind has a marked influence upon
the vegetation of the dune regions, although for the most part its

action is upon the environment directly and upon the plants only

more or less indirectly. Wind increases the evaporation of water

from the ])lants, but many of those which are modified to reduce trans-

piration have an abundant supply of water, so, at least to a certain

extent, such modification is inherent in the species and is not pro-

voked by the direct effect of the environment.

Influence of Lake Michigan

Lake Michigan exercises a leveling influence upon the region in

so far as temperature is concerned. The most evident influence is,

of course, upon the shore itself, which in places is built out and in

others is torn down. This has had a very marked effect upon the

beach associations, which will be discussed in the proper place. The
fluctuations of the lake within the last sixty 3'ears are shown in

Plate XLIII. Tidal waves are of rare occurrence (May 12, 1905,
and April 29, 1909). They may violently modify the vegetation, but

they do not occur sufficiently often nor are they sufficiently powerful

to permanently modify it. Such waves are seldom over 1.5 meters

*The state of affairs in which hiuiius-forming matter is so rapidly o.xidized

that no humns is formed.



261

high, and they are so short in their dnration that tlie fringing dune
has practically always been able to protect the land behind it. Once
the average lake level is sucii that the water is at the foot of the ridges
and prairies, as at Kenosha, no vegetation can prevent the steady cut-

ting which gradually eats away the ridges, prairies, and marshes.
Piers are built to combat this erosive action, but as a rule they merely
retard it and do not stop it.

General Description of the Region

The region lying between the Glenwood ridge on the west. Lake
Michigan on the east, Kenosha on the north, and Waukegan on the

south is very shallowly crescent-shaped. Its northern and southern
boundaries are marked by the extensions of the Glenwood ridge into

the lake as cusps. The length of the area is about 25 kilometers with
a width of from 0.4 to 1.6 kilometers. The elevation above Lake
jMichigan level varies from 0.8 to 9.0 meters. The soil is sandy
throughout.

As seen from the Chicago and North Western railway, which
skirts the western edge, the different parts of the region give the fol-

lowing general impressions : From Waukegan to a kilometer north

of the Lake County pest-house the land is characterized by marshy
swales separated from one another by very low sandy ridges. Li

no place are these ridges two meters above the level of Lake Michi-

gan. The vegetation is essentially prairie-like. It is very monotonous
in appearance, except during July, when the lilies are in bloom,

and during September, when it is covered with blazing stars. The
swales are uniformly occupied with swamp grasses and sedges, all

of which appear \ery much alike from the train. There are, at very

long intervals, scraggy trees which hardly break the monotony.
North of this area is another which, though of the same physio-

graphic character, gives an entirely different impression because of

the groves of pines that occupy the ridges. In consequence this por-

tion is termed the area of the pines. It is bounded on the west and
north by arms of the Dead Lake. Formerly the extent of this area

was much greater both north, south, and west; but upon those sides

it is being reduced by cutting, burning, and by natural successions,

while the fringing dune and the lake fomi its eastern boundary.
From the Dead Lake north to Kenosha is the area of greatest

extent. It is \\ooded, but in this case the trees are oak instead of

pine. There are many blowouts, those towards the north being

larger and slightly more numerous than those in the southern part.

The interridgial depressions, which arc not so low as those towards



262

the soutli, are, for tlie most part, wider, and are occupied by prai-

rie rather than by marsh plants. At the IlHnois-Wisconsin state line

the innemiost oak ridge has been cut away, leaving an area of level

sandy ground, one kilometer in width, from the lake to the bluff, in

which the highest elevation above Lake Michigan is scarcely 0.5

meter.

Nearer Kenosha occurs the last oak ridge (PI. XLIV, Fig. i),

which is quite wide and has several large blowouts in its sandy soil.

The end of this ridge is about a kilometer south of Kenosha.

It is being rather rapidly cut into by Lake Michigan. A little

north of the end of this ridge, and protected by it on the south and

west, occurs the only traveling dune of this area. It is very small

m comparison with those at the head of Lake Michigan. The part

between the oak ridge and the railway track is a sodded, sandy plain.

Just south of Kenosha measures have been taken to prevent the

rapid cutting away of the shore that had been going on. Conse-

cjuently the natural conditions have been destroyed. A little north of

ICenosha the Glenwood ridge has been cut into by the lake, and there

the region under consideration terminates.

Associations: General Consideration

In the naming of the ecological units there is still a confusion of

terms. In this article the name "association" is used to desigiiate

these units; and by an association is meant a group of li\ing forms

whose epharmony (ability to live with other forms in a given en-

vironment) enables them to live together as a uniform or homo-
geneous area of definite biotic composition.

Although animals are not given consideration in this article, it

must not be forgotten that they are an essential part of the associa-

tion, especially the smaller animals. Their ecological relationships

and correlations have, in general, not been sufficiently worked out

to accord them their proper consideration.

The term association rather than foniiatioii has been used for

the name of the ecological unit because of its priority* and its nat-

ural fitness. The term formation, as originally proposed by Grise-

bach,f was clearly intended to connote a broader group than the simple

ecological units which he mentions but to which he does not apply

a name directly. To use the term formation as the name of the

*HuMBOLDT, 1807. Essai sur la Geographie des Plantes, p. 17.

tGRiSEBACH, 1838. liber den Einfluss des Klimas auf die Begrenzung der

Natiirlichen Floren. Linnaea, 12:159-200.



263

ecological unit, as several modern writers nave done, is clearly a mis-

interpretation of Grisebach's statement. Warming (1909) definitely

uses the word association, which he explicitly states is not synony-
mous with Grisebach's "formation" but is included tmder it,*

Approaching the question from an analytical standpoint, Warm-
ing (1909: 140-145) defines a formation as "an expression of certain

defined conditions of life" which "is not concerned with floristic dif-

ferences," and an association as "a community of definite floristic com-
position within a formation" ; to which he adds : "it is, so to speak,

a floristic species of a formation ivhich is an ecological genus". The
ecological unit (association) is equivalent to the taxonomic unit

(species). Just as species are grouped to form a genus and genera

are grouped to forni a family, so are associations grouped to form
a formation and formations grouped to form a province. If neces-

sary, an association may be divided into consocies, in like manner as

species are divided into subspecies.

Of the apparent properties that ecological associations and taxo-

nomic species have in common, Haq^er (1906: 33-34) gives the fol-

lowing very pithy statement: "There are many analogies be-

tween habitat-groups and taxonomic groups, such as species, though

the latter are mutually exclusive categories and the former often are

not. For instance, both are able to be discovered, described, named,

and associated with certain type-localities. Records of both may be

preserved by descriptions, photographs, measurements, and other

means. Both have their diagnostic characters, with more or less va-

riation and intergradation. Both have passed through processes of

evolution, are self-perpetuating, and are liable to disappear through

geological or climatic changes or the works of man. New ones may
also originate, suddenly or gradually. Both have more or less def-

inite geographical distributions and regions of best development.

Both are capable of being subdivided, combined, or relegated to

synonymy, with the increase of our knowledge concerning them.

Habitat-groups, like species, can also be aggregated into larger cate-

gories analogous to genera and families".

Just as genera and species present difficulties of delimitation, so

do formations and associations. The difficulties of ecological classi-

fication show many points of similarity, and require fully as much

*For a detailed discussion of tlie questions involved the reader is referred

to the following articles

:

Smith, Robert. On the Study of Plant Associations. Nat. Sci., Vol. 14. 1899.

Warming, E. Occology of Plants, p. 139-148. 1909.

Moss, C. E. The Fundamental Units of Vegetation. New Phytologist

9:18-53, 1910.



264

study and experience for solution as do those of taxonomic classi-

fication. The criteria that have been used in delimiting and classi-

fying associations have been almost as various as writers upon the

subject.

Jaccard (1902:350) says, "Im allgemeinen ist der Bestand be-

stimmt durch die dominirende Art oder Arten". He was the first

to set up a mathematical criterion for distinguishing associations.

The association- or community-coefficient (Gemeinschaftscoefficient)

is obtained by dividing the number of common species, in the two

areas under consideration, by the total number of species in them.

For example, area A has 100 species, area B has 120 species, 60 of

which are common to the two areas. Then ^qq i ^-,q _ i^q
= 37-5

per cent, the community coefficient. For areas which are in the same
association and in the same locality this coefficient ought to be fairly

high. That even this method has its limitations Jaccard recognized

when he said, "Sie entsprechen zwar gewissen Differenzen in den

okologischen Bedingungen der verglichenen Territorien, aber es

besteht zwischen deni absoluten Werth dieser Differenzen und dem
der Gemeinschaftscoefficienten keine mathematische Proportionalitiit."

The same method was independently arrived at by. Professor S. A.

Forbes in a statistical study of Illinois Fishes.*

Besides the floristic composition told by mathematical methods,

associations are usually appreciated by any or all of the following

characteristics : (
i ) the presence of one or more dominating spe-

cies, (2) the presence of tension lines at their boundaries, (3) the

presence of evidence of dynamic succession, usually shown at or near
the tension line, (4) the presence of a uniform environment, (5) the

inability of species of different associations to mix, and (6) the pres-

ence of similar vegetative forms and environmental adaptations.

The association itself is composed of one or more principal or

dominating species, tenned the doiitiiiant species, which give the fun^

damental character to the association. In some associations the dom-
inant species may be the only species, but more usually the interstices

between the plants of the dominant species are occupied by what are

termed secondary species. Frequently secondary species by their

showiness give the color tone to the association. Where this varies

from season to season, these different appearances are termed the

seasonal aspects. Succession occurs when, in a given area, one asso-

ciation displaces another. Successions trend toward a definite cli-

*0n the Local Distrilnuion of Certain Illinois Fishes: An Essay in Statistical

Ecology. Volume VII of this series, Article 8.



265

matic association which, if conditions were ideal and sufficient time

were allowed, would occupy the whole of the given area. The series

of associations which succeeded one another from bare ground to the

climatic type is known as a genetic series. It is not necessary, how-
ever, that successions in a given area should proceed according to

the nomial genetic series. Mishaps of various kinds are continually

occurring to prevent this. Successions are recognized primarily by

the presence of pioneer or relic species within a given association. A
pioneer species, as its name implies, is a species of a given association

that can invade a genetically lower association, and a relic species

is a species of a preceding association which remains after a success-

ful invasion, thereby giving a clue to the situation. From this it

follows that a complete association—if one may be allowed to use

that tenn in this connection—consists of dominant species, secondary

species, whose varying seasonal dominance produces seasonal aspects,

invaders or pioneer species of a succeeding association, relics of a

former association, together with such ubiquitous species, which seem

to have little or no restriction placed upon their distribution, as may
occur there.*

Successions form die most satisfactory approacii to the ecological

study of a region, and for this reason it may be well to give the sub-

ject brief consideration. As mentioned above, successions are often

easily recognized in an association by the presence of pioneer or relic

species. When associations within one fomiation are concerned, suc-

cession usually takes place by the invasion of the secondary species of

the invading association, and the succession may be said to be com-

pleted when the dominant species have made their appearance. In

the case of the invasion of an association of one formation into an

area occupied by an association of another formation, invasion is ef-

fected by the dominant species, with the subsequent appearance of

the secondary species. As one would naturally expect, invasion of

one formation into another takes place through the pioneer associa-

tion, which is characterized by a paucity of species, relatively speak-

ing, and, consequently, in such an area the vegetation consists of the

dominant species of the invading association with such of the species

of the invaded one as can live under the new conditions. These
secondary species are existing there as relics, yet they comprise vir-

tually all of the secondary vegetation. This same principle holds akso

*For further discussion of the association consult

:

Clement.s, F. E. Research Methods in Ecology. 1905.

C0WLE.S. H. C. The Causes of Vegetative Cycles. Bot. Gaz. 51 :i6i-i83, Mar,
igii.



266

for the invasion of one province by another; that is to say, the dom-

inant species of the invading association are the pioneer species in the

invasion. Many other general principles concerning succession might

be given, but as Adams has summed up "Some Principles of Suc-

cession" tlie reader is referred to "An Ecological Survey of Isle

Royal, Lake Superior," pages 146 to 149, (1909) for their state-

ment. A relic species exists in a given association because it occupies

ground which as yet is not tenantable by any of the species of the

succeeding association, rather than because the succeeding association

can not displace the relic. An invader occupies more nearly its opti-

mum habitat, but the relic lives where the other plants seem not to

be able to develop. The disappearance of the relic usually takes

place with the death of the individuals, whereupon the bit of ground
which it occupied may be taken up almost immediately ; or again

—and many instances are at hand—the spot may remain bare for

some time to come. Some relics modify the structure of their vege-

tative parts and continue for a long time after the invasion has been

completed. Junipers and Rhus canadensis illinoensis (sumac) are

two very good examples of this class of plants.

The naming of the associations has been approached from many
different view points, but the most natural course seems to be to use

the name of one or more predominating species, and, accordingly,

that method is adopted in this article. In cases where another inves-

tigator has found associations clearly the same as those of the Beach

area, the name that he used will be given first consideration, priority

being regarded in so far as the fitness of the subject will pennit.

The Lower and Middle Beach Associations

As the waters of Lake Michigan receded, a sand beach was ex-

posed. This furnishes the starting point of a genetic series of asso-

ciations which is known as the beach succession. Bare sand and the

water of the streams and lakes are the two initial points of primary

successions in this drea.

THE CHLAMYDOMONAS ASSOCIATION

The classification of lake beaches has usually been founded upon

a physiographic basis, in which the features distinguished are lower,

middle, and upper beaches. The "lower beach" of Lake Michigan has

been defined by Cowles (1899:113) as "that zone which is situated

between the water level and the line reached by the waves of common
summer storms." He gives an alternate definition on page 114; "It



267

might almost be defined as that portion of the beach which is devoid

of vegetation." The lower beach of the Beach area physiographic-

ally speaking, exists in two modifications, one consisting, of a very

gradnal slope, which may be concave, and the other of a relatively

steep slope. Beaches of the first type are but very little elevated

above the average le\el of Lake Michigan. The sand is damp, either

to the very surface or, at least, to within one or two millimeters of

it. Just at the edge of the lake is a little ridge which permits water

to be retained beyond it. This water forms what is termed a beach

pool. Being almost at the level of the lake, drainage back into the

lake is very slow. In rainy seasons or at times of frequent north to

southeast winds the beach pools may remain for a long time. During
the ordinary growing season the sand is never sufficiently dry to be

blown about in the wind. In beaches of the second type, the slope

is much greater and the water from each wave drains away very

rapidly. As a result, two to three centimeters of dry sand form the

surface. This sand is, of course, easily blown about in the wind.

Neither of these two types of the lower beach bears vegetation

of a penuanent nature. In beaches of the first type, the one-celled,

motil alga, Chlainydonionas, together with Oscillaforia, may occur in

such numbers as to cause the wet sand to appear green. This con-

stitutes the Chlainydonionas association. These algae occur also in the

waters of the lake, but their optimum habitat seems to be the beach

pools which occur near the outlets of sewers or near the mouths of

creeks bearing sewage. (See Plate XLIV, Fig. 2.) The sand

around the pool is mushy and rather greenish in color. The ridgelet

between the beach pool and the lake is very low (10 cm. at most)

and very narrow. Every north to southeast wind will cause the

waves to run over the ridge and flood the pool with sewage-laden

water from the nearby sewer. This constant flooding, together with

the rather frequent rains, resulted in a permanent jjool during the

season of 1909. Small snails appeared, and u])nn them as well as

upon other living forms the sanderlings shown in the figure are

feeding.

Aside from the algae, vegetation u])on the lower beach is jnirely

accidental. One such case is that of a large willow log which was

broken in three pieces and washed up to the edge of the lower beach

by the tidal wave of April 29, 1909. The original source of this log

is not known, for nowhere in the Bcacli area are there willows of

such size. The logs lie just within the reach of every ordinary wave.

Succeeding storms have partially covered the logs with sand, which

is constantly kept moist by the waves. From the logs themselves,



268

shoots have grown up six decimeters. Whether these logs will with-

stand the winter storms and, together with some wreckage near by,

originate another ridge remains to be seen.

Another case of accidental vegetation on the lower beach is very

temporary in duration and extent. It occurs south of Kenosha, where
Lake Michigan is cutting into the prairie. Some prairie plants, nota-

bly loosestrife {Lytliniin alaliini), are carried bodily from the prairie

and are occasionally left stranded with their root systems in the damp
sand of the lower beach. They remain living until washed away al-

together by a succeeding storm.

The part of the lower beach which is devoid of plants comes next

into consideration. The area is bare because plants can not obtain a

footing there—and not because they will not grow there. The rea-

sons which are given briefly by Cowles (1899:114) and more fully

by Jennings (1909:310) are as follows: the alternate washing by
storm waves and the severe drying out under the sun, combined with

the washing about of the sand when submerged and its blowing

about when dr}^, prevent the establishment of any plants whose seeds

actually do germinate. After a rainy spell of two or three days' du-

ration, such as August 13-15, IQ09, it is not at all a diflicult task to

find, scattered over the slightly damp sand, seeds which have begun
to germinate. With the reappearance of the sim and the drying of

the surface sand, these partially germinated seeds dry up and are

blown about by the wind. That living forms, however, can maintain

themselves on this area is clearly shown by the industry of the turn-

stone (Arcnaria interpres), which, during its brief sojourn in this

region in the spring and fall migrations, is continually occupied in

ferreting out the small insects and other animals which are found
under the pebbles.

The junction of this area with the portion of the beach continually

washed by the waves is the location of the willow log and wreckage

previously mentioned. One piece of wreckage, a little over a meter

in length, projects somewhat over a decimeter into the air. The
ordinary waves just fall short of its lakeward side. On the landward
side, stretching southwestward, is a miniature dune of sand in which

are growing the following plants: Junipcrus Iwrhoiifalis—a single

healthy shoot, 3 cm. in length, growing next to the wreckage; Prii-

nus pitmila (sand cherry)—a sprawling shrub; Poa coinpressa (Eng-
lish blue-grass)—a few plants; Potentilla aitscrina—one plant with

five radiating runners ; Equisetum arvense—a few plants ; a com-
posite which was so depauperate as to be unrecognizable ; and a con-

volvulaceous plant, together with the exposed roots of CaJainoz'ilfa

Io)igifoHa. A wagon track through the dune explains the planting of



269

the Potciililla, the composite, tlie Bquiscttiiu, and the convolvulaceous

plant, for they were growing in tlic hottoni of it. The nearest source

for the Jiiniperus was about a hundred meters away, froni which the

seed may have been carried by the gulls which are abundant on the

beach and occasionally are seen in the heath. Close to the lee (south-

west) side of another piece of embedded wreckage in this same vicin-

ity was a straggling plant of Xanthium commune (cocklebur).

Taking all these facts into consideration, it seems e\ident that a

new ridge is being thrown up. The pieces of wreckage were prob-

ably lodged there during the \iolent storm and tidal wave of May 12,

1905. The juniper came in in the backwash of that storm or by some
other agency, as suggested above, in 1906, as it appeared to be three

or four years of age (1909). The storm and tidal wave of April 29,

1909, did not dislodge the wreckage nor the juniper. It added ma-
terial that can assist in the formation of a ridge. Progress towards
that end, howexer, is very slow.

The Chlaiiiydonioitas association is entirely identical with the

Chlaiiiydoiuonas formation of Jennings at Cedar Point (1908:313)
and at Presque Isle (1909:310). Occasional presence of the alga

was reported by Cowles near Porter, Indiana, (1899:114). This

association, together with the plantless area, composes what MacMil-
lan termed the "front strand."

The Cakile-Xanthium Association

From the upper limits of the open sand of the middle beach, and

therefore out of reach of the ordinary storm-waves, an area of

sparsely \egetated sand stretches inland. This is the location of the

Cakilc-Xaiitliiiiiii association. The !and^vard Ixnmdary of this area

is usually the fringing dune.

Physical Emironiiient.—The physiographic characteristics of this

association are fully discussed by Cowles ( 1899:1 1
5-1 17) and by Jen-

nings (1909:311). The middle beach, as Cowles designated it, lies

"between the upper limits of the summer and winter waves." It is

dry in summer, and dififers from the lower beach only in that it is not

subject to the mechanical violence of the waves during the growing

season. The soil is, for the most part, sand whose grains vary be-

tween 0.2 and i.o mm. in diameter. It is exposed to the full force

of wind and sun, and conse(|uently it is very dry nearly all of the

time. During the daytime the sand may become very hot (60° C),
but it cools off rapidly during the e\'ening. Although the upper few

centimeters are so very dry, the sand beneath is always moist and

may even be wet.



270

Ecological Characteristics.—The plants that persist in this as-

sociation possess certain general characteristics: (i) they are an-

nuals, because perennials are uprooted during the winter storms;

(2) their disseminules are comparatively heavy, so that altho they

are blown about they are not blown away; (3) their seeds have suf-

ficient vitality for sending their tap-roots through 4-10 cm. of dry

sand to the moist sand below; and (4) their aerial parts are low,

radiately branching or bushy, narrow-leaved, and frequently succu-

lent. In other words, the plants of this association are subjected to

the se\'erest kind of xerophytism. Such a habitat, hydrophytic be-

neath the surface of the ground and xeropyhtic above ground, is

termed dissophytic by Clements.

Development.—In the Beach area the middle beach, to use Cowles'

term, exists in two modifications. Towards the southern end, it is

highest at the boundary line separating it from the lower beach,

from which it slopes very gradually down to the fringing dune—

a

slope of but a few centimeters at most. Towards the north the nar-

row middle beach slopes upwards and abruptly gives way to the much
higher (2-4 meters) fringing dune. Here the middle beach is sub-

ject to continuaJ removal of its sand by the prevailing westerly winds.

As the winds are in the westerly half of the compass much more than

half of the time, the formation of extensive or high dunes is impos-

sible on account of the lack of sand. The re])lenishment of the sand

of the middle beach takes place during the easterly storms, of which
there are but a few each year. Such storms, as a rule, are accom-
panied by precipitation, which further retards tlieir power of bring-

ing up sand from the lake. One may judge of the amount of sand

that such a storm may pile up by the effects of the storm of July 30-

31, 1908, in which the wind was east for a day and a half. A ridge

some 20 meters wide and 0.4 meters high was piled up in front of

the mouth of the Dead River, completely closing the channel—

6

meters wide and 0.5 meters deep—which that river had had the day
previous. And this does not begin to compare with the amounts
blown up on the southern and eastern shores of Lake Michigan. Some
sand is blown up during the winter unless the shore is ice bound. At
that season there is a noticeable transfer of sand from the northern

parts, where it is held by the season's vegetation, towards the south-

ern parts, where north of the Waukegan piers it is building the shore

out into the lake.

The southern part is more wind-swept because protected on the

landward side by only a very low (at most 0.2 meters) fringing

dune. It is characterized by extreme openness of vegetation. The



271

plants that occur, always at very widely separated intervals, are sea-

side spurge (Euphorbia polygonifolia), cocklebur (Xaiitliiiiin com-
mune), and sea rocket (Cakilc cdcntula), in abundance as named.

Each of these plants has to contend with a continual exposure of its

root system by the remo\-al of sand. Euphorbia polygoiiifolia usually

escapes this by living in depressions. If growing on the le\'el, how-
ever, it forms a dense mat which holds the sand within its compass,

building up a miniature dune aljout two centimeters in hight and
sometimes twenty centimeters m diameter. (See Plate XLV, Fig-

ure I.) If the blowing is too vigorous, the plants will succumb,

and it is not unusual to find dead, curled-up plants of this species

rolling about in tiie wind. There is apparently no adaptation in

Cakilc for the protection of its root system, but Xantliiiini is adapted

by growing procumbent with only the apical four to seven centimeters

projecting into the air. The spread of leaves around the stem aids

in the formation of a small, temporarv dune which protects the root

system from exposure. Even then plants have been found in which

there was a distance of 6-10 cm. from the exposed bur, from which

the plant had germinated, to the point at which the root was covered

with sand. This indicates that considerable sand had been removed.

Pieces of driftwood on the l^each are often the starting points for

small, temporary dunes. Occasionally a plant of Xanthiiiiii couuiiune

will fix such a dune for a season. In the vicinit\- of Beach, where

the middle beach is very narrow and protected by the fringing dune,

the characteristic plant is Eiiplwrbia polygoiiifolia. This plant is

most abundant where there are pebbles to afford it protection from

the wind. Cakilc cdcntula occurs only at rare intervals, while Xan-
fhiuin is virtually absent.

During the season of 1910, which was characterized by the ex-

treme duration of a protracted drought, the water-level of Lake

Michigan was very noticeably lowered. This made the wave action

on the ground occupied by this association virtually nil. In addition

to a normal abundance of the usual dominant species, there were

the following secondary plants, whose growing habits were somewhat

similar to those of the dominant sjiecies : Cyclolouia atriplicifolium,

Russian thistle (Salsola kali tcuuifolia } ; bug-seed [Corispcrmum

hyssopifolimn), cottonwood {Popubis dcltoidcs), and Salix syrticola.

AH of these plants were characterized by the extreme length of their

secondary roots. These spread radially from the small bushy plants,

giving the planr command of the water supply from an area eiglit to

fourteen feet in diameter. The roots were quite strong and could be

easily pulled up in lengths of f(nir to six feet. The plants themselves



272

seemed to be smaller and more succulent than usual, but the stems
were thicker, and in the case of plants which are more or less pubes-
cent when young the pubescence was retained and frequently devel-

oped into villousness. All of these modifications were direct results

of the dryness of the summer.

LIST OP THE SPECIES OF THE CAKII.E - XANTHIUM ASSOCIATION

Dominant Species

Cakilc cdcntula Xanthium coininunc

Euphorbia polygoiiifolia

Secondary Species

Corispenuv.m hyssopifoliuiit Cycloloiua atripUcifoliiiiii

In\ading species (all of which are relatively scarce and are not

met with every year)

Salsola kali toiuifolia Salix syrticola

Populus dcltoides Potcntilla anscrina

On the normal middle beach, only the first three of the dominant

species, mentioned above, are present. North of Winthrop Harbor,

however, where the ridges and swales are being washed away by the

waves, several other species are found on the middle beach. Tlieir

presence is both accidental and temporally. The more frequent of

such plants are blue \-ervain (Verbena liastata), mullen (Verbascum
tliapsiis), sandbur (Ccnchriis carolinianus), .strawberry (Fragaria

zirginiana), white clover (Trifolinm repcns), smartweed {Polygo-

num persicaria) , Potcntilla anscrina, Polygonum acre, Panicum capil-

larc, Acjiida tuberailata subnuda, Polygonum lapatliifoliuiu, horsetail

(Equisetuin arz'cnse), and sand-bar willow (Sali.v longifolia). In

other places were the following additional species: blue grass (Poa
pratcnsis), Juncus tenuis, Canada thistle (Cirsiuui arvensc), Lythrnm
alatuin, Radicula palustris, and red clover (Trifoliu)n pratcnse). Al-

though these plants occur within the limits of the Cakilc-Xanthiuin

association, they do not properly belong to it for the following reasons.

Surrounding their roots, there is always more or less prairie humus,
which is sometimes only about the individual plants. In some places

there is a strip of prairie which, when undermined by the waves,

slides down on the middle beach, carrying with it whatever plants are

growing in it. Later, these strips are buried by a few centimeters of

drifted sand. The ])lants usually persist through the one season but

do not grow the next year. The burying process may keep up dur-



273

ing the season. In general this is Haljle to kill ])rairie plants within

the summer, but, in a few cases, Panicmn capillarc, Aciiida tnbercii-

lata subHiida, Trifoliinii rcpcns, and Salix loiigifolia will keep pace

with the incoming sand.

Since these species which constitute the deri\'ed element of the

association can under no circumstances commence to grow on the

middle beach, and since their presence there is to be accounted for

solely by physical displacement of the soil u])on which they were
growing and has absolutely no successional value, one can not say

that they are a real part of the association.

The Middle-Beach Pool Associations

In describing the middle beach (see under Development, page 270)
it was mentioned that in the southern part of the area its slope from
the lower beach was downward toward the lake-level. Just a little

north of the docks at Waukegan, the beach has reached the level of

sand which is permanently moist clear to the surface. Standing wa-
ter is not usually present throughout the season, and so the beach

pool is not permanent. This is the situation to which three groups of

plants give such a definite floristic character that they must be termed
associations, small in area and isolated though they are. In genetic

order these are the Jtincus alpiniis hisignis, the Triglochin pahtstris,

and the Carex ocdcri pttinila - Cypenis rnndaris associations. These
groups of plants are not of frequent occurrence in this region. Al-

though they usually occur isolated from one another, they show suf-

ficient successional relationships to indicate that they are three asso-

ciations, rather than consocies of one association as Jennings (1909:
352) treated them.

THE JUNCUS ALPINUS INSIGNIS ASSOCIATION

The lowest of these associations, the Junciis alpiiiits insignis, has

been found in typical form only in e-xce])tionally dry years, such as

1908 and 1910, when it occupied the dried-up bottoms of beach

pools. This JuncHS grows in small tufts, thoroughly dominating the

association. With it are seldom any secondary species, and when
they do occur they are of very minor importance.

LIST OF THE SPECIES OF THE JUNCUS ALPINUS INSIGNIS ASSOCIATION

Dominant Species Secondary Species

Juuciis alpinus iitsii/iiis Bideiis vulgata



274 •

Invading Species

Scirpus aniericanus Triglochiii palusfris

THE TRIGLOCHIN PALUSTRIS ASSOCIATION

This association is present every year. It normally occurs along

the margins of the beach pools or in moist sand in other depressions.

The individual plants of the Triglochiii, which comprise about 70
per cent, of the area, grow close together in small tufts. The tufts

themselves are separated by intervals of two to three to ten centime-

ters. Toward the landward side, where the tufts are still farther

apart, the secondary species of this association occur. They are pi-

oneers of succeeding associations, the most important of which is the

/uncus balticus liftoralis, which grows in higher gromid than does

the Triglochiii.

LIST OP THE SPECIES OF THE TRIGLOCHIN PALUSTRIS ASSOCIATION

Dominant Species Relic Species

Triglocliiu [^alustris Juuciis alpiinis iiisignis

Invading Species

Jiincus balticus liftoralis Juncus torrcyi

Potentilla anscrina • Scirpus americaiuis

Populiis dcltoidcs (a few small Cypcrus rivularis

seedlings under 12 cm. high)

THE CAREX OEDERI PUMILA - CYPERUS RIVULARIS ASSOCIATION

This association occupies a still higher position on the beach than

the preceding one. It occurs around beach pools, but is more likely

to be found in swales between the ridges than on the lake beach it-

self. Wherever it occurs, it is characteristic of moist rather than

wet sand. It is usually submerged for a time in spring, but the

ground becomes dry by the begiiming of summer. This association

is characterized during" the ditYerent seasons by well-developed aspects.

Throughout the aspects, plants belonging to the sedge family are the

dominant species ; Carrx oedcri puinila in late spring and early sum-

mer, Rynchospora capillacca leviscta during the serotinal season, and

Cypcrus rivularis during the fall. Secondary species are somewhat
more numerous in point of numbers than in the two previous associa-

tions. Most of them are invaders of the different associations that

may follow this one.



275

LIST OF THE SPECIES OF THE CAREX OEDERI PUMILA-
CYPERUS RIVULARIS ASSOCIATION

Dominant Species

Carex ocdcri puinila Cypcnis rirularis

Ryiiclwspora capillacca Icz'iscta Carer aitrca

Fii)ibristy!is castanea Elcocharis acinniiiafa

Rauimciilus scclcratus

Relic Species

Triglochin palitstris

Invading Species

Potentilla anserina Salix syrticola (small plants)

Jitncits balticus litforalis Lobelia kaliiiii

LinuDi virginianmn Utriculana corniita

THE SABATIA-LINUM ASSOCIATION

Immediately above the preceding association and sending oul

many invaders into it, is the Sahatia-Linnm association, which is al-

most the exact counterpart of that found by Jennings (1909:355)
on Presque Isle. One of the dominant species of this association,

Sabatia angiilaris, occurs in the general region around the head of

Lake Michigan, but is locally absent in the Beach region. The pres-

ence of this association is usually an indication that a given area of

ground will be occupied by prairie rather th.an by forest associations.

LIST OF THE SPECIES OF THE SABATI.\-LINUM ASSOCIATION

Dominant Species

Linuin virginianmn

Secondary Species

Lobelia kalniii Campanula aparinoides

Utricularia cornuta Spiraiitlies cernua

Aster ptarinicoides Gerardia paupercida

Carex craivei Liparis loeselii

Gentiana proccra (small plants)

Relic Species

Eleocharis aciiiiiinata Carex ocderi pitniila

Rynchospora capillacea levisefa Carex aitrea



276

Invading Species (of relatively frequent occurrence)

JuucKS balticiis litforalis

Invading Species (of ratlier rare occurrence)

Salix longifolia Paniciiin sp.

Sali.v glaucopliylla Arctostaphylos uva-ursi

Salix syrticola Petalostemum purpureuni

THE JUNCUS BALTICTS LITTORAUS ASSOCIATION

One of the first indications of the first type of upper beach, as

Cowles (1899:167 et seq.) terms that part of the beach which is en-

tirely witliout \va\'e action throughout the year, is the presence of the

rush Junciis ballicus litforalis. It grows from straight rhizomes

which may be over three meters in length. The lines of plants cross

and recross each other in every direction. Expansion on the land-

ward side is ecologically impossible because of the closed association

behind it. Progress out on to the middle beach is limited only by
the action of the waves in winter and by tlie winds which keep un-

covering the outennost rootstalks. As the lines grow outward the

shifting sand is retained around the bases of the plants. It may even

form embryonic dunes to the hight of a few centimeters. This work,

however, is nearly always destroyed when the westerly winter winds,

with nothing to impede them, carry the sand back into the lake. The
Junciis itself does not seem to be able to fix the dunes, but it is a

pioneer that enables dune-fixing plants to gain a foothold on a low
and level beach like that which, in the southern part of this area,

extends from Beach to Waukegan. There is no Jiiiicits where the

slope of the shore is 15° or more. The lakeward side of this associa-

tion is composed of just the one species, Jidicks balticiis litforalis.

In the middle and in the landward side other plants appear. The
most abundant of these is silverweed (Potcntilla aiiserina), of which
more will be said in connection with the following association. Small
straggling plants of Sali.v syrticola occur at intervals, but as a com-
ponent part of tliis association they are not well developed. Occa-
sionally a dwarfed, small-leaved plant of Cottonwood, Populus del-

toidcs, may be seen. Because of the deficiency of nutriment in the

soil the cottonwoods grow very slowly—sometimes not more than a

couple of centimeters in a season. Scirpus aiiiericaniis occurs here

more frequently than in the Triglocliiii paliisfris association, but still

is not abundant. It has a remarkable tendency to grow in a spiral

form when it grows in the sand.



277

The /uncus balticus littoralis itself possesses this tendency, but to

a less marked degree. The presence of the Scirpus is conclusive

proof that wet sand is close to tiie surface.

LIST OF THE SPECIES OF THE JUNCUS BALTICUS LITTORALIS

ASSOCIATION

Dominant Species

JiDiciis balticus littoralis

Relic Species

Triglochin pahistris Cyclolouia atriflicifolium

Cakilc cdcntula

Invading Species

Potcntilla aiiscriiia Elyuius canadensis

Salix syrticola Scirpus amcricanus

Populus dcltoidcs

In addition to the part that the Jiincus plays in building up the

beach, it has an important role in retarding the storm waves in their

attack on the shore-line between Kenosha and Winthrop Harbor. Its

etYorts are only partially successful as Figure i, Plate XLVI, illus-

trates. The relic dune* (A) in the center of the figure and the two
at the left, mark the limits of the grassy sand plain in 1905. This

plain is usually separated from the lake by a very dense growth of

Juncus balticus littoralis. The width of this Juncus association is from

one to three meters. It is separated from the grassy plain by a narrow

tension zone of Potcntilla anserina. The interwoven mass of rhizomes

of the Juncus protects the sand from sliding. As a result there is nor-

mally a perpendicular bluff of i.o to 1.4 meters' elevation at the lake.

Repeated buft'etings of the lake wear through the Juncus in spots.

This affords an opening to the grassy plain behind, with which vio-

lent waves make short work. The limit of the wave action is due to

the loss of power to move sand after the waves have proceeded over

a stretch of beach. The retreating waves carry back with them sand

from the rear of the Juncus. After about four years of such action

the beach line has the appearance shown in Figure i, Plate XLVI. In

the center of the figure is a relic dune. Its elevation abo\-e the water
is the same as that of the grassy plain in the foreground. This is il-

lustrated by Figure 2, Plate XLV. The sides of these relic dunes

Gates. F. C. Relic Dunes, A Life Hi.'^tory. Trans. 111. Acad. Sci., Vol. Ill,

1910, pp. 110-116.



278

are coated with a dense mat of exposed rhizomes of Jiiiicus. At "C"
in the figure is a Junciis dune in one of the stages of obHteration.

The flora of these interesting relics is very uniform. Jnncus bal-

ficiis littoralis is tlie characteristic species and occupies 95 to 99
per cent, of the area of the caps in Figure i, Plate XLVI. The fol-

lowing are infrequent in their occurrence and irregular in their dis-

tribution: evening primrose (Oenothera rhombipctala), Russian
thistle (Salsola kali teiiiiifolia), sandbur (Ceiichnis caroliiiiaiuis),

silverweed (Potcntilla aiiscriiia), Sporoboliis cryptandnts, dogwood
(Cornus sfolonifera), and Calamovilfa longifolia.

Proceeding southward from the portion shown in Figure i, Plate

XL,VI, the shore-line begins to curve somewhat to the west and is not

subject to so much wave action. The rifts in the /uncus association

become less frequent and of less and less importance as the shore dips

away from the direct attack of the waves. The sand is piled at the

base of the /uncus rhizouics so that the bluff is concave. The associa-

tion still contains over 90 per cent, of /uncus balticus littoralis, but

secondary species are a little commoner and more sandbur {Cenchrus

caroliniaiius), Cornus stolonifcra, Ptclca trifolia, Canada thistle (Cir-

siuin^ ari'cnse), Oenothera rhonibipctala, and balm of Gilead {Popu-

lus candicans) are present.

Besides characterizing an association, /uncus balticus littoralis

grows in a majority of the other associations of the Beach region.

It will be given consideration accordingly under them. Notwith-
standing its apparent disregard for habitat it rarely shows any
modifications in form in the habitats in which it is evidently a relic.

THE POTENTILLA ANSHRINA ASSOCIATION

From the /uncus balticus littoralis association the sand slopes up
gradually to the Sali.v syrticola or fringing-dmie association. This

slope is characterized by a rather dense growth of low plants of which

silverweed {Potcntilla aiiscrina) constitutes from 70 to 90 per cent.

It may be termed a tension-line association, and separates very dis-

tinctly the fringing dune from the /uvcus association. Potentilla an-

serina grows in each of the three associations, but it shows its max-
imum de\'elopmcnt in the Potcntilla association. In the bordering

associations the size of the individuals varies to a minimum and their

number to zero.

Potcntilla anserina spreads very rapidly by means of runners

which radiate from the parent plants. At quite regular intervals

of from one to two decimeters each runner sends out roots and leaves.



Tlie new growth decreases in size with increasing distance from the

center. Any accident received by the runners causes separation into

independent plants, from which new runners may extend. Pofen-

tilla can not contend with the wind. It is rather easily killed, either

by sand being blown away from its roots or by being buried in drift-

ing sand. In the spring, before there is a carpet of vegetation over

the ground, the young plants are to some extent protected from the

wind by the bushes of Salix syrticola and the dead stems of Jiincus

balficus littoraUs. Once a carpet is formed, there is little danger of

damage from the wind.

If protected from wind and still connected with the parent plant,

runners may proceed through rifts in tlie Juncus, out upon the middle
beach, where they may develop roots and leaves in the usual way but
of smaller dimensions. During the season of 1908, when there was
an unusually small number of heavy winds, many long runners de-

veloped in this way. A number of them w^re severed, resulting in

the gradual starvation of the young plants, thus isolated upon the

middle beach. This was probably due to the deficiency of food ma-
terial there—a fact which has often been commented upon. The
season of 1909, with its heavy surf and strong wind storms, prevented
any such development of runners.

The secondary species of this association are not many in either

number of species or of individuals. Without exception they arc

obviously under the usual size. This also is due to the lack of nour-

ishment in the sand. The commonest of these species is Juncus balfi-

cus lifforalis. A few J. alpinus i)isif/nis occur as relics where the Po-
tentiUa has successfully in\'aded the Triglocliin palusfris association.

The Triglochin may also remain as a relic but it is less liable to per-

sist.

LIST OF THE SPECIES OF THE POTENTILLA ANSERIN.\ ASSOCIATION

Dominant Species

PotentiUa anscrina

Secondary' Species

Juncus baliiciis liltoralis (which is also a relic)

Relic Species

Juncus alpiiius insigiiis Triglochin' palustris

Invading Species

Salix syrticola Populus delfaides (1-2 dm. high)

Calaniorilfa longifolia Salix longifolia

Panicuin I'irgaluni



280

In beaches wliich are being destroyed, sucli as the region between

Winthrop Harbor and Kenosha, a narrow tension association of Po-

tentilla aiiscrina separates the grassy plain {Poa coiiiprcssa associa-

tion) from the very low ridge of a very dense growth of Jnnciis hal-

ticns littoralis. In the course of the destruction of the shore, as has

been mentioned above, there is exposed an area of open sand between

the sand-plain and the relic dunes. (See Fig. i, Plate XLVI.) For

the most part, this area is devoid of plants but in slightly sheltered

places, Potentilla comes in and spreads out radially, forming mats a

few meters in width and several meters in length. The leaves are

usually half buried and the runners can scarcely keep above the sand.

It may be for this reason that here the internodes of the runners are

so short. With it are seldom any secondary species. At the edge of

the grass on the sand-plain (Fig. i, Plate XLVI) is a well-developed

association of Potentilla, and mixed with it are Sporoholus cryptan-

driis and sandbur (Cd'nchriis caroliiiiaiius). This makes a denser

vegetation during the growing season than the grassy sand-plain it-

self shows, and effectually prevents any blowing during that period,

thus protecting the grassy plain. During the winter, when the sand

is rendered mobile with the drying of the Potentilla, a general south-

ward movement of the sand takes place in sufficient quantities to be

noticed from year to year.

The Dune Form.\tion

Landward from the beach formation occurs the dime formation.

This has been so frequently and so well described, (e.g., Cowles,

1899), that only a brief summary of the characteristics need be given

before dealing with the associations. The essential conditions for

dunes are wind, dry mobile sand, and a nucleus to allow the sand to

accumulate (cf. Warming, 1909:263).

Ecological Characteristics.— (Cf. Cowles, 1899:106-111). The
sand-dune is a very xerophytic habitat because of the agencies that in-

crease transpiration and at the same time keep down the water sup-

ply, such as intense light and heat and strong winds. The water

supply for sand-dune plants is deficient because water passes through

sand very readily and but a small amount is retained in it. To this

may be added the low nutritix'e value of the sand. On account of

the insolubility of the sand grains and the easy access of air, organic

matter which otherwise would form humus is rapidly oxidized. Wa-
ter continually passing through the sand waslies away even the less

soluble food constituents (Livingston, 1903:14). A sand-dune, how-



281

ever, is not dry throughout. The sand to within a few centimeters
of the surface is moist. The layer of dry sand which acts as a very
good non-conductor of heat pre\ents the entire desiccation of a dune.
Because of this, vegetation there is possible.

Adaptations of the Vegetation.—The characteristic adaptation of

sand-dune plants is found in the extreme development of the root

system in comparison with the aerial parts. To meet the constant

shifting" of the sand, which may uncover the roots, they are capable

of producing adventitious shoots. Because of this, the plant can

sometimes move a considerable distance in keeping pace with the

sand. Sand-dune plants usually co\er quite a little ground, and thus

protect themselves from exposure of their roots because of the blow-
ing sand. The grasses that inhabit the dunes are perennials, and they

are frequently tufted. The mere presence of some of these grasses

on the upper beach may often be the starting-point of a dune.

The aerial parts are clearly developed in response to the extremely

xerophytic habitat. The leaves are firm in texture, with stomata

well protected by the position of the leaves or by a protecting cover-

ing of hairs. Often the leaves are long and narrow and curled or

folded to reduce transpiration. The inflorescence is frequently pro-

tected in the upper sheaths until it is virtually fully ready for polli-

nation.

Plants as Dune Builders.— (Cf. Cowles, 1899:175 et seq.)

Plants may live on a dune and yet add nothing to the life of a dune.

They will accumulate sand during a season and form miniature or

embryonic dunes, but as soon as the plants die down in autunin the

sand is again mobile. Such dunes very seldom last during the winter,

although many of them are formed during the growing season. They
are the "annual dunes" of Cowles (1899:177). To endure from
season to season a dune must be fixed by perennials, particularly of

the group known as sand-binders. It is well known that owing to

the persistence of the vegetative parts in winter such plants have con-

siderable ability to prevent sand from shifting. For a dune to grow
larger the sand-binder must be able to respond easily to changing

conditions ; and it must not be killed by exposure of its root system

nor by the burial of its stem. To make the dune more extensive it

must be able to spread radially by rhizome development, thus devel-

oping the dune in expanse at the same time that the upward growth
of the stems is developing it in altitude.

Location in the Beach Area.—The sand-dunes occur a little be-

yond the limit of winter wave-action. They are more general in oc-

currence and better developed in constructive beaches. Nowhere in



282

this region are sand-dunes well developed. This is because the pre-

vailing winds are westerly, while the lake, from which the sand

must come, is to the eastward of the beach. The largest dunes are

about four meters high. They are protected from westerly winds by

woods of pine or oak. Towards the northern and southern parts of

the area, where there is no protection from winds, the dunes are sel-

dom more than four decimeters in hight. All but one of the dunes
in the area are fixed dunes, either permanently or for a season only.

Traveling dunes, such as occur along the southern and eastern sides

of Lake Michigan, are absent because the prevailing westerly winds
merely take away any loose sand and carry it back into the lake. The
one traveling dune is nine meters high, and is protected from westerly

winds by oak woods. In order to have any permanent dunes what-
soever the sand must be fixed by vegetation.

The Dune Associations

Tlie different dune-forming plants give a more or less character-

istic apearance to the dunes on which they occur. The dune-fonner
is the all-important plant in the dune associations. Only a very few
other species are capable of withstanding such a severe habitat, and
as a consequence the dune associations are poor in species. As soon

as the pioneer species begin to accumulate humus, invaders appear

and assume possession, while the pioneers advance onward, in gen-

eral, towards the lake. The process is, however, very slow, and is

greatly hindered by severe wind storms and tidal waves.

Dune associations are usually independent of one another, and the

dune complexes are built up in part by the growth of individual

dunes. When this occurs, succession takes place which leads to the

formation of the climax dune vegetation, as the juniper dunes may
be designated.

THE CALAMOVIIvFA DUNE ASSOCI.'VTION

The sand-binding grass, Calaiiiovilfa longifolia, plays the most
important part in initiating new dunes on the upper beaches. This

grass is a most efficient sand-binder, and it will commence its growth
under more adverse conditions in this region than will any of the

others. The root system is extensive and forms a very dense tangle,

as shown in Figure i, Plate XLVIII. This plant always grows in

tufts, and as soon as the leaves appear sand begins to be caught

around the stems and lower leaves. The dune soon takes the shape

shown in Figure 2, Plate XLVII. From tlie windward side the dune



283

slopes quite gradually up to the highest point in the center of the

clump, from which the slope is more gradual down to the leeward.

After severe wind storms the leeward trail may be over a meter in

length. A change of wind, however, soon changes its position.

During the winter the dead standing stems with their leaves pro-

tect the dune in a measure from ordinary winds and storms. On the

more open upper beach this protection is inadequate, and the return

of the growing season finds the sand level with some exposed roots

to show the former location of the Calamovilfa dune. But a short

time is needed to reconstruct the dune when the growing season is

once commenced. In less exposed situations the dunes persist over

winter.

The Calamovilfa dunes are a conspicuous feature of the vegeta-

tion of the lake shore in the central part of the region, yet the dunes

are never large in size. They spread radially quite easily but they

do not grow very much in hight. A Calamovilfa dune a meter high

is uncommon. The usual altitude is from three to six decimeters.

Higher dunes are formed by plants whose ecesis can be accomplished

in a Calamovilfa dune but could not have been on the normal upper
beach.

The outcome of the growth of these dunes is usually the forma-

tion of a ridge running parallel with the line of wave action. As
additional ridges are built up nearer the lake, the Calamovilfa remains

as a relic along the crest of the ridge. In such places it sometimes
exhibits the growth form known as fairy rings. Succeeding associa-

tions, however, finally bring about its disappearance. The secondary

species of this association are very few in number and, in general,

unimportant in value.

LIST OP THE SPECIES OE THE CALAMOVILFA DUNE ASSOCIATION

Dominant Species

Calamovilfa longifolia

Invading Species

Andropogon scoparins Petalostemuin piirpureum f. arena-

Prunus ptimila Hum
Elyimis canadensis Quercus velutina (rarely)

Salix glaucophylla Vitis vidpina (one plant, 3.5 meters

Poptdus candicans long)

THE AMMOPHILA ARENARIA DUNE ASSOCIATION

Because there is so little sand carried from the lake, this associa-

tion of dune plants is very scarce in this region. Ammophila arciiaria



284

is a plant that grows best where there is an abundance of blowing

sand. In such situations it builds dunes to a hight of several meters.

In this region the Ammophila dunes are in no case more than a meter

high. The dune has a very gradual slope, which is steeper on the

landward side. The plant spreads in lines and does not form clumps

as Calamovilfa does. Ammophila exceeds all other sand-binding

grasses in the ability to grow upwards with the accumulation of the

sand, .^t the same time the aggregation is so open that, in this re-

gion, it permits the sand to be carried back into the lake almost as

fast as it is accumulated by the plant. This is the exact reverse of

conditions prevailing in the Calamovilfa dunes, where the close bunch-

ing of the grass and the usually persistent dead leaves at the base of

the stem permit a more prominent heaping up of the sand.

Ammophila dunes are pioneers of upper beach vegetation, but they

will not commence so near the drift beach as will the Calamovilfa.

On the other hand, Calamovilfa can capture the Ammophila dunes
and replace the plants by which they were formed.

The Ammophila dune association is so poorly developed in this

area that an adequate description of it is not possible from the data

at hand. An extended description is given in a paper by Cowles

(1899:179-181). The secondary species that occur have scarcely any-

thing to do with the growth of the dune. They merely represent

beach species whose seeds have lodged among the Ammophila stems.

Lathyrus maritimiis, the beach pea, is the most abundant and best de-

veloped. Its procumbent stems trail in and out between the Am-
mophila stems for several decimeters. Like the other secondary

species, it occurs just over the crest, as viewed from the lake. The
main part of Figure 2, Plate XLVIII, is occupied by an Ammophila
dune.

LIST OF THE SPECIES OE THE AMMOPHILA DUNE ASSOCIATION

Dominant Species

Ammophila arenaria

Secondary Species

Calamovilfa longifolia Potcntilla anscrina

Lathyrus maritimiis

Relic Species

Euphorbia polygonifolia Xanthium commune

Invading Species

Calamovilfa longifolia Sali.v longifolia ^
Prunus piimila Solidago graminifolia



285

THE SALIX SYRTICOLA DUNE ASSOCIATION

In the southern part of the region occur the low fringing dunes

which are tenanted by the willow, Salix syrticola. They are low flat

dunes, just a little out of the reach of the winter storms. They tend

to grow in width rather than in hight, and consequently this associa-

tion is one of the first to make a permanent vegetation on the beach.

The plant itself grows as a straggly bush, sufficiently dense, ap-

parently, to cover the ground with vegetation but not to prevent a

strong wind from carrying away sand that may have accumulated

at the bases of the stems. Because of this the hight of these dunes
depends upon the amount of protection that they have from the west-

erly winds. From Waukegan to the area of the pines, where there

is no such protection, the Salix syrticola dunes are from two to four

decimeters in hight. When protection is afforded by the pines the

dune will keep pace with the blowing sand to a hight of about three

meters. Only a few plants of this willow, however, are able to con-

tinue their growth upward with the accumulating sand, and the ridge

is broken up into a dune-complex in which only a few of the dunes
belong to this association.

At the southern end of the area, where the beach is low and very

level, seeds of this willow germinate in the Jiincus balticus littoralis

association. The plants are larger in the Potentilla association, and
reach their average development in size on the low ridge just back
from it. This ridge is the typically developed Salix syrticola dune.

In this part of the region occur the majority of the secondary species,

virtually all of which are relics or invaders.

A little farther north where the beach is still level, although
sloping upward all the way from the lake, the Salix syrticola dune,
composed of the dominant species only, occupies the lakeward front.

There is more blowing sand there and each plant is partly buried.

The plants continue their advance lakeward as fast as they are per-
mitted by means of their underground stems.

LIST OF THE SPECIES OF THE SALIX SYRTICOLA DUNE ASSOCIATION

Dominant Species

Salix syrticola
~

Secondary Species

Blyiints canadoisis Lathyriis iiiariliiiii/s (rare)

Salix longifolia Salix glaiicopliyllii

Populus deltoidcs f i m. high)



286

Relic Species

Potentilla anserina Calmnovilfa longifolia (not com-
Juncus balticus littoralis mon; it usually occurs as a lit-

Xantliiitiii coiiiiiinnc tie hill, built up 1-2 dm. above
its surroundings)

Invading Species

Andropogon scoparius Potentilla fruticosa

Solidago graminifolia Equisetmn hiemalis

THE PRUNUS PUMII.A DUNE ASSOCIATION

Entering into the composition of the dune-complex to the east-

ward of the pines are several steep mounds surrounded and capped

by sand cherry (Fnmiis puinila). This plant is a very efficient dune-

holder, but no examples of stages in dune formation by it were found.

The occasional presence of a Calainovilfa at the summit indicates

that, in this region at least, Prnnns pnniila dunes are formed by the

replacement of a dune-originator. The fruit of the Prtmus is eaten

by a few species of birds among which are two, Uie song sparrow and
the tree sparrow, which occasionally frequent the clumps of Calaiiio-

znlfa. Once the Primus is started, sand can be easily held by its dense

growth. This is too dense for secondary species, but where there is a

break, a young Popidtis candicans may be present. Occasionally on
one of these dunes there is alongside of the Priiiuts pitiiiila a bush of

dogwood (Comits stolonifera), which has much the same habits as

the Primus. The presence of the Corniis is due directly to birds, as

this species is avevectant. The robin seems to be the most probable

agent, as it has been obsei'ved eating the drupelets, and has been seen

on the Prnnns bushes while drying after a bath in the lake. The dis-

tance traversed by the dogwood amounts to nearly a kilometer.

On account of the dense growth of the dominant species, a Pru-
nus pnmila dune remains an isolated unit in the dune-complex. In

case of the death of the Prnnns the sand which it has held is again

mobile, and a few wind storms will effect its removal.

LIST Ot THE SPECIES OE THE PRUNUS PUMILA DUNE ASSOCIATION

Dominant Species

Prunus pumila Cornns stolonifera (infrequent)

Secondary Species Relic Species

Popidus candicans Calanwvilfa longifolia (not

common)



287

THE POPULUS CANDICANS DUNE ASSOCIATION

In a restricted area between Beach and Zion City occur the dunes
of maximum hight. They are sumiounted by narrow groves of bahn
of Gilead (Fopiiliis candicans) . The tree trunks show no evidence

of being buried. On the other hand, at the ends of the association

there is every evidence to show that sand is being blown lakeward,

and, to a sHght degree, landward, upon an adjoining prairie or heath,

as the case may be.

Popidits candicans is a plant which facilitates the growth of dunes

but it does not originate tliem. The plants of the dunes are all trees

of average size. The young plants, when present on dunes at all, oc-

cur among other species, especially with Pritniis puiiiila. By far the

greater number of the young plants occur in the heath and the Liatris

scariosa associations. There they grow, and by their shade the den-

sity of the ground flora is reduced. As this disappears sand is set

free to the wind, and may then form a ridge dune. These dunes are

quite similar to those found by Jennings (1909:338) on Presque Isle.

There, however, it is Cottonwood (Populns deltoides) that is the dune'

nucleus. Po/Jif/H^ (/f/^oiV/ej occurs in the Beach region along the mar-
gins of either permanent or temporary lagoons but the individuals

are separated and do not show a tendency to become dune- formers.

A Popidus candicans dune is shown in the background of Figure 2,

Plate XLVIII.

LIST OF THE SPECIES OF THE POPULUS CANDICANS DUNE ASSOCIATION

Dominant Species Secondary Species

Popidus candicans Primus puniila

THE ELYMUS CANADENSIS DUNE ASSOCIATION

Dunes of this type are infrequent and of little importance in this

region. They are low (3 dm.) with a rather steep front towards the

lake and a very gradual slope away from the lake. The crest is occu-

pied by wild rye (Elynius canadensis) and the slope by that species

mixed in with Sporoholus cryptandrus and Artemisia caudata. West-
ward of these dunes is an open area from which sand has been re-

moved by man to the lake-level. Tiie Elymus dunes keep the lake

from flooding the area and the spring rains from running directly

into the lake.



288

LIST OP THE SPECIKS OF THE ELYMUS CANADENSIS DUNE ASSOCIATION

Dominant Species

Elynius canadensis

Secondary Species

Sporobolus cryptandrus Salix longifolia

Euphorbia polygonifolia Cycloloina atriplicifoHuiu

Euphorbia corollata Asdepias syriaca

Rhus toxicodendron Panicum virgatwn

Artemisia caudata

Relic Species

Cakilc cdentula

THE JUNIPERUS DUNES ASSOCIATION

When a small dune has been formed by some of the sand-binding

plants, such as Calamovilfa, Prunus pumila, or, less frequently, An-
dropogon scoparius, either one or both of two species of Jnniperus

may come in and replace them, forming what is called the juniper

dune. Bearberry (Arctostaphylos uva-ursi), a heath plant, may be

present, but in this region it shows a preference for the sides ratlier

than the crests of dunes. These plants, Arctostaphylos and the two
species of Juniperus, seldom intermingle but form adjoining families

in the same association. There seems to be no evidence as to which
juniper appears on a dune first. Juniperus horicoiitalis, however, is

by far the more abundant on the dunes, although Juniperus coiniuimis

depressa is just as well developed. It is characteristic of juniper

dunes to have the sides as well as the crest densely matted with vege-

tation. Juniperus horizontalis is especially adapted for this (see PI.

XLIX, Fig. i). Its prostrate stems form a dense matwork of vege-

tation in both winter and summer, which retains considerable sand.

The junipers themselves easily keep pace with the infiltration of sand,

and by growing outwards permit the dune to grow radially at the

same time that it is growing in hight. This figure shows a place

where the wind is demolishing the dune. The Calamovilfa which ap-

pears midway at the left was carried there when the crest gave way to

undermining. These dunes reach an altitude of three to four meters.

Higher growth is difficult because most of the sand-blowing winds
are parallel to rather than at right angles with the axes of tlie dunes.

Juniperus communis depressa dunes are less frequent and more
gently sloping than those of Juniperus horicontalis. Their sides are



289

much more frequently blown away by the wind. In view of this, un-

less the sides are fixed with Junipenis horizontalis or Arctostaphylos,

a Junipenis commimis depressa dune is liable to be blown away, thus

forming a break in the line of dunes through which the wind carries

sand on to the heath behind them. At the same time, adjoining dunes

of Juniperits horizontalis are undermined until the exposed side be-

comes covered with vegetation.

The junipers are the most efficient dune-builders in this region,

but they can build dunes only where their westward side is protected

from the prevailing winds. Normally the junipers are mat-formers
in the heath association, which will be considered later, but in the

presence of blowing sand they meet the change of condition by be-

coming dune-builders. These dunes must be closed associations, since

any open place on them would be seized upon by the wind and the re-

moval of the dime effected. The vegetation being dense and com-
pletely covering the ground, secondary species, with the exception of

relics on the crests, do not occur. Of these relics, which were the

nuclei about which the dune originated, Calamovilfa is the most fre-

quent, with Primus puniila second, and a very few plants of Andro-
pogon scoparius and a single one of Cornus stolonifera.

LIST OF THE SPECIES OF THE JUNIPERUS DUNES ASSOCIATION

Dominant Species Relic Species

Junipenis horisontalis Calamovilfa longifolia

Junipenis coinrniinis depressa Primus piniiila

Arctostaphylos iiva-ursi Andropogon scoparius

Cornus stolonifera

Miscellaneous Dunes

In addition to the associations given above, which occupy about

97 per cent, of the dune areas, there are isolated dunes, each one of

which is characterized by a rather definite association of plants. In

each case the plants are more typical of other associations, but they

grow within the range of blowing sand and consequently dunes may
be formed around them.

THE populus-salix dune association

But two well-marked examples of this dune association, which has

been described from Presque Isle by Jennings (1909), occur in the

region. In both cases the dunes are low and are formed on the east-



290

em border of the bunch-grass prairie, to be described later. One
of these dunes was occupied by the following species : cottonwood
{Popuhis deltoides) (2 meters in hight), Salix glancophylla, Salix

syrticola ( a relic), Calaiiioz'ilfa lojigifolia, and Potentilla fruticosa.

The other example had the following plants : Scdix syrticola, Juncus
balficits littoraUs, Eh'nnis canadensis, Salix longifolia, Populus del-

toides, and Potentilla anserina.

Once in a while a well de\'eloped Salix glancophylla or Salix long-

ifolia will form miniature dunes. The branches bend down to the

ground, and beneath their shelter sand and debris gradually accumu-
late. In the debris are seeds of various plants, notably the winged
ones of species of Populus and Salix. In rifts where sufficient light

may be had, a number of plants which could not obtain a foothold on
the open sand may get a start. The following species were observ'ed

:

strawberry {Pragaria znrginiana) , rock cress (Arabis lyrata), flea-

bane (Brigcron philadelphicus), silverweed (Potentilla anserina).

Panicnm inrgatum, Artemisia caudata, Zizia aurea, touch-me-not

(Impafiens biflora), dandelion (Taraxacum erythrospennnm), and
sweet clover (Melilotus alba). Seedling Populus deltoides were also

present, which indicates that a Populus-Salix dime is being formed.
Populus deltoides itself when growing on sand in this region does not
form dunes. Species of Salix, which afford a ground protection to

retain sand, at the same time serve to catch Populus seeds. Normally
a thicket should be formed, but as yet the ground is too poor in food
materials to support the mesophytic species of the thicket association.

THE SALIX GLAUCOPHYLLA DUNE ASSOCIATION

A few dunes formed entirely by this plant were observed near
Kenosha, one of which is shown in Figure 2, Plate XLIX. The
dunes are low and elliptical in shape, while the major axis, which
runs north-northwest, is about twice as long as the minor axis.

THE PANICUM VIRGATUM DUNE ASSOCIATION

During the growing season a small dune may be built up around

a tuft of Panicum virgatuui, but such dunes are temporary, as they

do not withstand the winter. As a rule these dunes have no other

species than the Panicum upon them, but occasionally Arabis lyrata,

Salix syrticola, Poa compressa and Poa pratensis occur around the

edges of the tuft of Panicum.



291

TI[R ANDROPOGON SCOPARIUS DUNE ASSOCIATION

This grass normally grows on level ground, but it may come in

on the sides of dunes originated by sand-binders such as Calamovilfa.

Witli the death of the Calamovilfa, Aiidropogon scoparius is left in

full possession. It is efficient in holding the dune, but further growth

of the dune ceases. Such dunes are at most five decimeters high.

Near Waukegan, in a place where sand has been freed from
gravel, there was left a gravel movmd about two meters high. The
summit and nearly all of the sides are tenanted by Andropogan sco-

parius stools, in the interstices of which are several sand plants, as,

for example, Arabis lyrata, Petalostemimi piirpurenm f. arenariuni,

Lithospcniiiiin giiiclini, etc. It has the general appearance of a devel-

oped dime, such as Jennings has described from Presque Isle, but the

manner of its origin was evident.

THE POPUIvUS-SALIX-CORNUS THICKET DUNE ASSOCIATION

This dunelike condition exists near the state line where the lake

is attacking the shore. It is not a developed dune, but the result of

sand being blown in upon the Populus-Salix-Cornus thicket which is

being cut into by the lake. The thicket reacts to the inblowing sand,

however, by becoming a dense mass of liana-entwined vegetation with

an advance-guard of Salix longifolia to check the advancing sand.

Such thickets are well nigh impassable on account of the network of

lianas, which in this area are wild grape (Vitis vulpina) and Virginia

creeper {Psedera quinqiiefolia). Sand-bar willow (Salix longifolia)

easily keeps pace with the blowing sand, but succumbs to the violence

of wave action as the shore is gradually washed away. With the

Salix longifolia are associated a few prairie plants, the roots of which

are in sod buried beneath the sand. A few of the commonest are

loosestrife (Lythnim alatwn), Panicuui capillare, white clover (Tri-

folium repens), blue vervain (Verbena hastata), mullen (Verbascum
ihapsus), Polygonum lapathifolimn, sandbur (Cenchrns carolini-

anus), and Canada thistle (Cirsiuni arvense), which in this and other

places forms small dunes five to six centimeters in liight.

THE BETULA ALBA PAPYRIFERA DUNE ASSOCIATION

But two examples of this kind of a dune occur in this area. The
sides are very steep and are effectually protected by a small grove of

seedling trees of white birch.



292

RELIC DUNES*

Dunes form one of the typical stages in the construction of beaches

and tliey may also be one of the stages in the destruction of a vege-

tated beach, when they may be termed "relic dunes." (See group of

dunes, PI. XLVI, Fig. i.) The vegetation north of Winthrop Har-

bor is bordered on the lakeward side by a low ridge which supports a

very dense growth of Juncus balticus littoralis. When the lake begins

to cut into the beach it washes away sand from the Juncus, leaving an

exposed bluff of densely intertangled roots. In weak spots the waves

are able to wash their way entirely through the ridge of Juncus to

the grassy plain beyond, wliich is easily destroyed as far as the waves
have power. In places the Juncus is left as a mound with its sides

perpendicular and densely coated with exposed roots. This is an early

stage of a relic dune. (For such dune, shown in detail, see PI. XLVI,
Fig. 2.) As wave action continues, the onwash and the backwash of

the waves, in combination with the wind, reduces the dune from the

appearance of "A" (Fig. i, PL XLVI) to that of "C," in which the

sides are sloping. These summer secondary stages look very mucli

like ordinary dunes except that they are more or less coated with ex-

posed roots. In course of time the dune is entirely washed away.

During winter the disruptive power of freezing water is an important

agent in the breaking up of the dunes. The effect of a severe frost

immediately following a heavy rain upon one of these dunes is shown
in Figure i, Plate XLVII.

These dunes are prominent features of the vegetation of the beach

from the state line to Kenosha. With the Juncus are associated a few

plants of relatively little importance, such as Sforobolus cryptandrus,

Russian thistle (Salsola kali tenuifolia) and dogwood (Cornus sto-

lonifcra). Besides the Juncus relic dunes, there is also a single ex-

ample of a relic dune formed by Jnniperus communis depressa (see

"D," Fig. I, PI. XLVI). Its sides are not so steep as those of the

Juncus, and most of the vegetation is on the lakeward side. The sand

that accumulates somewhat in the rear of the dune is not washed away
rapidly because the dune is so near the limit of wave power. During

the course of the next few decades there will be eight or ten of these

Jnniperus relic dunes, formed by both Juniperus communis depressa

and /. hori::ontalis.

THE MAN-MADE DUNE

In order to protect the golf groimds at the southern edge of Ke-

nosha from blowing sand, a long dune about two meters high has

*Sce p. 277.



293

been constructed and fixed by planting willows upon it. For the most
part it is tenanted by species of willow, especially Salix longifolia and
S. glaucophylla. The bushes form a fairly dense tangle about 1.4 me-
ters high, and mixed with them are individuals of wild rye (Elvmus
canadensis), horsemint {Monarda punctata), butter and eggs (/.iw-

aria vulgaris), wovmwooi (Artemisia caudata) and yarrow (Achillea

millefolium). In a few places the dune is fronted by Juncus balticus

litforalis. Upon the west side of the dune the sodded ground extends
to its base. The south end is not sufficiently well protected, and con-
sequently the wind is undermining the willows to some extent.

THE TRAVELING DUNE

For reasons given before, this kind of a dune is not a feature

of the region; in fact there is but one present in the area. Its bight

above the lake-level is nine meters, and a few oaks have been partially

covered by it.

The Upper Beach Associations

the artemisia- panicum association

This association, which is so wide-spread on Presque Isle and is

of general occurrence along the shores of Lake Michigan, is but

poorly represented in this region. A majority of the species men-
tioned by Cowles ( 1899 :i68 et seq.) occur upon it, but from 40 to 60

per cent, of the area is taken up by invading plants of the bunch-

grass association, which borders and is extending rapidly into it.

Location and Physical Characteristics.—The area which stretches

back from the fringing dunes, is largely composed of sand whose
grains are about 0.5 mm. in diameter. The relative amount of sand

decreases in going away from the lake. At the same time the rela-

tive amount of gravel increases. The change is uniform, though
gradual. The Artemisia-Panicum association occupies the sandier

parts of the upper beach, and thins out quite rapidly as the amount of

gravel increases. The reverse of this is true with respect to the bunch-

grass association. The sand is somewhat mobile, but not much so be-

cause of protection by tlie fringing dune and by the vegetation of the

bunch-grass association. Water is near the surface and is easily

available, but food materials dissolved in it are low in amount. The
aeration of the sand, aided by the relatively large spaces between the

grains and the sudden changes of temperature, is very thorough,

which leads to rapid eremacausis and consequent absence of humus.
Ecological Characteristics.—Except for the absence of wave ac-



294

tion there is very little difference ecologically between this area and the

middle beach. The habitat is dissophytic, because the underground
parts of the plants are in mesophytic to hydrophytic condition accord-

ing to the water content of the soil, while the upper parts are sub-

jected to rather severe xerophytism. The desiccating effect of the

wind and sun are met by adjustments in the plant structure (cf.

Kearny 1900:276-280).

The Association.'—The association is an open one, in which about

30 to 40 per cent, of the area is vegetated. From 30 to 50 per cent,

of the vegetation is occupied by the dominant species, wormwood
(Artemisia caudata), which gives a grayish tone to the soil. Cowles

(1899:168) says that the most characteristic plants are Artemisia

caudata and A. canadensis. In the Beach region, only the A. caudata

is present. In a similar area near Rogers Park, Chicago, a few miles

south, both species occur. Another dominant species, Panicuni vir-

gatum, which Jennings found at Cedar Point and Presque Isle, is of

relatively little importance in this association in this region, although

it occurs not infrequently. Its place is taken by Sporobolus cryptan-

drus, which grows in clumps somewhat like a bunch-grass. Its

growth habit is illustrated by Figure i, Plate L. This plant, how-
ever, is usually more characteristic of blowouts.

These three character species occupy about 95 per cent, of this

area in typical situations of this association. Typical examples are,

however, rather rare in this area. The best developed of them is

about a kilometer north of the Lake County pest-house. There, this

association is eight to ten meters in width and approximately twenty

meters in length. Usually the invader, Andropogon scopariius, gives

a decided character to the appearance of this association, in which it

grows at intervals of two to three meters.

Of the other species which Cowles has listed as characteristic of

this association, only four specimens of Pitcher's thistle (Cirsiuni

pitcheri) have been found. A very few plants of beach pea (Lathy-

riis maritluius) occur here, although it is commoner on the lee slopes

of the Amnwphila dunes. A spurge {Euphorbia polygonifolia) is

fairly abundant, although it can not be so characteristic as on the

middle beach. Evening primrose, Oenothera biennis, does not occur

in this association, and a grass (Agropyron dasystachyuni) does not

grow in the region.

Secondary species occur more or less throughout the association,

but are most abundant near to the margins, where the prairie element

has commenced to invade. They are not usually numerous, but fre-

quently, because of their bright-colored flowers, seem to be nearly



295

dominant floristically. Such plants characterize the seasonal aspects

of the association. The late-vernal and estival aspects are given by

the orange flowers of puccoon {Lithospernmm gntelini). This plant

has a very long (3 or more meters), bulky tap-root, from the crown
of which grow many spreading stems. It does not occur so frequently

in the typical parts of the association as it does in the tension line,

which the bunch-grass is rapidly pushing outwards. The serotinal as-

pect is characterized by the blooming of the yellow flowers of a gold-

enrod {Solidago nenioralis). This plant also is much more charac-

teristic of the bunch-grass sand areas. The autumnal aspect is given

by the blooming of Sporobolus cryptandriis and of Artemisia caiidata.

In addition to those secondary species that give character to the

different seasonal aspects, there are a few other species, typical

of different associations, that are of importance in showing the past

stages and in indicating the future successions.

LIST OF THE SPECIES OE THE

Dominant Species

Artemisia caudata

Panicum virgatum

Secondary Species

Cirsium pitcheri

Lathynis viaritimus

Eupliorbia polygonifolia

Lithospermwn gmelini

Arenaria stricta

Relic Species

Euphorbia polygonifolia

Primus pimiila

Invading Species

Andropogon scopamis (at inter-

vals of 2-3 meters)

Lithospcrmuui gmelini

Arenaria stricta

Solidago nenioralis

Liatris scariosa ( few )

ARTEMISIA-PANICUM ASSOCIATION

Sporobolus cryptandriis

Cycloloma atriplicifolium

Bqnisctitni hieniale

Arabis lyrata

Petalostemum pnrpureum f . are-

nariiim

Calamovilfa longifolia

PotentiHa friiticosa

Poa compressa
Aster dumosiis

Arctostaphylos uvorursi (few)
Jimiperus horicontalis (a few

patches)

THE BUNCH-GRASS ASSOCIATION

The Andropogon scopariu.s Consocies

Location and Physical Characteristics.—Immediately westward of



296

the usually poorly developed A'rtemisia-Panicmn association lies a

more or less gravelly or pebbly area, whose vegetative appearance is

characterized by the stools of Andropogon scoparius. The physio-

graphic appearance gives every indication that the area was at one
time part of the beach. Later it was covered with drifting sand, and
it is now being gradually uncovered by the very slow movement of the

fringing dune towards the lake. Because of its past history it is

given the name, "fossil beach," in allusion to the corresponding geo-

logical term. The pebbles and the gravel of which its surface is com-
posed are all well-rounded and flattened, clearly indicating the former
presence of surf. The largest of these pebbles are about 15 cm. in di-

ameter and 2-3 cm. in thickness. Almost all of them are made up of

granites, quartz, and, less frequently, shales and sandstones. From
between them the wind has gradually removed the mobile sand, which
is taken to the lakeward side of the fringing dune. So much sand has

been removed that now the pebbles are very frequently perched upon
little hills a few millimeters in hight. Investigation has shown that

the sand in these little "tees," to use a golfing term, is virtually damp
clear to the surface. The pebble itself affords the tee protection from
the drying effects of the direct rays of the sun. In the protection thus
afforded, spiders as well as some small insects spend the hotter part

of the day. Rain drains very rapidly through this soil.

Ecological Characteristics.—What has been said of the ecological

characteristics of the Arteinisia-Panicum association will apply here

also. The habitat is dissophytic, but the above-ground part is not

quite so xerophytic as in the other association. Humification—rather

than eremacausis, which is the rule in the Arteniisia-Panicum associa-

tion—is beginning to take place. Lack of sufficient food material

seemed to be the most potent cause for the openness of the vegeta-

tion.

The Association.—The bunch-grass association is a typical prai-

rie one, and, of course, is better represented in areas farther west.

The bunch-grass association of tlie prairie vegetation is the pioneei

both of the prairie and the forest type of vegetation. It can maintain

itself on fossil beaches and readily invades the upper beach. Mean-
while it adds humus to the soil and prepares the way for successions

to a more advanced type of prairie or to a heath or to a forest.

Which succeeds, depends upon several factors, among which are

proximity, means of dispersal of the invaders, and the ability of the

invaders to effect ecesis. The association itself has for its dominant

species a grass which grows in tufts or bunches. According to the

specific identity of the bunch-grass, the association is divided into



297

consocies. Some of these have been described for southeastern South
Dakota by Harvey (1908) and for the IlHnois sand areas by Gleason

(1910). Of these consocies only one appears as a definite part of the

region in this area. That is the Andropogon scoparius consocies,

which has been described as a pioneer of prairie \egetation by Han'ey
(1908:287). There are, however, clear indications that other con-

socies have been represented which are now succeeded by forest as-

sociations. Some of the bunch-grasses, which were once dominant
species, are now relics, living as secondary species in the Quercus
velutina woods.

The association itself is open, since but 25 to 40 i>er cent, of the

area is vegetated. Approximately 90 per cent, of the vegetated area

is occupied by the dominant species, Andropogon scoparius. Tlie sec-

ondary species may be more numerous, but they are interstitials that

occupy very little surface. Figure 2, Plate L, shows the general ap-

pearance of the association throughout the year, and exhibits the

manner of growth of the dominant species.

Andropogon scoparius-—As sliown in Figure 2, Plate L, this grass

is a typical bunch-grass. The dead leaves remain over winter and until

the new leaves grow. They do not seem to be capable of retaining blow-
ing sand, and so this grass is not a dune-former. It can fix dunes,

however, but not until the dune has been built up by some regular

dune-former. The plant spreads radially, but very slowly as it has

no runners. The spreading continues until the diameter of the stool,

or bunch, is from 3.0 to 3.5 decimeters. It does not often grow larger

than this. Occasionally bunches are to be found in which the cen-

tral part is dead, the circle of stems aiound it forming a small fairy

ring. Other plants become established in the center, and tend to lead

to the gradual replacement of the bunch-grass. Arahis lyrata and
shrubby cinf|uefoil (Poten filia frtiticosa), an invader, are most fre-

quent in this role. Others that have been found so situated are

Arenaria stricta, Oenothera rhonibipetala, blue-eyed grass (Sisyrin-

chium sp. ?),and Artemisia caudata. In this area the bunches them-
selves are always separated, usually by about eight to nine decimeters

The more pebbly the area, the greater the tendency for the bunches to

be nearer together, but seldom closer than five decimeters. The bunches
which are invading the Arteniisia-Panicum are developed just as well

as those in the bunch-grass itself.

The area between the bunches is occupied by interstitials, which,

however, are not sufficiently abundant to prevent the sand from giv-

ing the general color-tone. In point of numbers rock cress (Arabis

lyrata) is most abundant. When it is well in bloom, in May, the



298

white flowers considerably lighten the general dull gray tone of the

dead leaves of the Andropogon. This is the vernal aspect. Next to

secure color prominence is L,itJiosperiniim gnielini, which blooms dur-

ing June and July. This plant is not actually abundant in the typical

part of the association, but its manner of growing and the abundance

of its brilliant orange flowers are easily misleading in determining

the importance of the species in the association. It is most abundant

near the tension line, towards the outside of the association. Al-

though this plant has neither dune- forming nor dune-fixing abilities,

it seems most at home where this association is invading the lower

parts of the dune-complex near Beach. There it occurs at frequent

intervals, without apparent discrimination between the lower places

and the sides of the dunes. Occasionally it is present on the tops of

some of the smaller diuies. Seedlings of this species can be found in

various situations, although they are most frequent in depressions.

The root system of Lithospennum gmelini can withstand a moderate

amount of either burying or uncovering, so that the plant can easily

tenant the dune-complexes of the region which are protected from
the westerly winds by the area of the pines. It seems to fulfill the

position of pioneer to the Andropogon scoparius consocies of the

bunch-grass association. Cycloloma atriplicijolkim , Petalostemum
piirpiireum f. arenarium, and Arenaria stricta play the same role, but

to a less marked degree.

The estival aspect of this consocies is characterized by the bloom-

ing of the Andropogon scoparius itself, and of the interstitial Petalos-

temum purpiireum f. arenarium (sand-prairie clover). The latter

species, which is typically a prairie plant, exhibits marked xerophytic

adaptations in several particulars—so much so that a detailed de-

scription is necessary, and it is here given in the form of a table.*

PETAIOSTEMUM PURPUREDM f. arenarium FORMA NOVA.



299

The appearance of the sand form is very different from that of

the prairie type, but the differences are due to the edaphic xerophytic

conditions under wliich it grows. In places where this association has

been succeeded by trees which have induced milder xerophytic con-

ditions the Petalostenmm, although still growing in nearly pure sand,

is about normal in appeararice. Figure i, Plate LI shows a plant of

this form in which the stems form an angle of from 5° to 15° with the

sand level. In some cases sand and debris have been piled up above the

crown, while sand beyond the protection of the stems has been blown
away. In such places the Petalostenmm, when growing prone, makes
a negative angle with the general level. In general the individual

plants grow apart, but on the gravel, where there is almost no ex-

posed sand, they grow so close together that the heads overlap and
form a tangled layer about a decimeter above the gravel level. Such
situations are frequent hiding-places for savanna and song spar-

rows. The heads of the Petalostemnm seem usually to be infested

with a small green caterpillar, and the leaves with tent-weaving

larvse.

In the serotinal aspect, Petalostemnm continues to dominate the

more gravelly parts, but in other places a goldenrod (Solidago nem~
oralis) comes into prominence. The bright white pappus of the fruits

of both Andropogon scoparius and Solidago item oralis are character-

istic of the autumnal aspect. Neither of these plants loses its seeds

until after the sharp winter frosts. With the return of winter the

association assvimes a dull gray color of dead leaves which resembles

in some particulars the arid brush-lands of the West.

List of the Species of the Andropogon scoparius Consocies of the

Bunch-grass Association

Dominant Species

Andropogon scoparius

Secondary Species

Arabis lyrata Aster scnccus

Arenaria stricta Blymns canadensis

Oenothera rhombipetala Cycloloma atriplicifoliitm

Litliospermum gmelini Hypericum kahnianum

Petalostemum piirpurcinn f. Oenothera biennis (very few)

arcnarium Pritnus pitmila

Solidago nenioralis Aster multiflorus

Euphorbia corolla ta Mosses (unidentified)



300

Relic Species

Artemisia caitdata Calanwz'ilfa loagifolia (asindivid-

Sali.r syrticola als rather than in bunches)

Salix g'laticophylla (not common) Sporoholus cryptandrus

Jnncus balticiis littoraHs (not

common)

Invading Species

Potentilla friiticosa Junipcrus communis depressa

Sisyrinchium sp. ? (few)

Populus deltoidcs (small) Jnniperus horizontalis (few)

Salix longifolia

The Sporobolus hbteroi,epis-Sorghastrum nutans Consocies

This consocies, which has been more widely extended in the past

than it is at present, is quite similar to ordinars^ prairie. For the

most part the consocies has been succeeded by Qucrais z'clutina, but

in a few places between the oak ridges there still remain small char-

acteristic areas of it. Four bunch-grasses are its dominant species

The two after which it is named are most abundant. The others are

Andropogon scoparius and A. ftircatus. The largest and most con-

spicuous of the bunch-grasses is Sorghastrum nutans, which grows in

tufts rather than bunches. It is, perhaps, the most persistent as a

relic in the association that has followed. Sporoholus hcterolcpis it-

self grows in rather good-sized bunches which are usually ringlike,

the open area in the center being a flat motuid of blackish dirt. The
stems and leaves are thin and wiry, and the plant as a whole has a

rather delicate appearance. In parts of this region this grass may
occupy 60 per cent, of the area. Andropogon ftircatus, which grows

in small bunches, aids in giving a general character to the area, but

it is the least important of the four bunch-grasses mentioned. It

seldom occupies more than 10 per cent, of the area, but it will per-

sist under the oaks almost as well as the Sorghastrum. Andropogon
scoparius, whose bunches have already been described, occupies from

30 to 50 per cent, of the area. It is smaller in size and does not give

so much character to the vegetation. It grows out in the open parts

of the association and, while it does persist in the Quercus velutina

association, it does so only in the open places. In the autumnal as-

pect these four bunch-grasses occupy about 97 per cent, of the area,

the remaining 3 per cent, being secondary species. Some of the lat-

ter are interstitials, as Arcnaria stricta; others are grasses, as Spartina

michaiixiana and Poa coiuprcssa; and still others are invaders from



301

nearby prairies and forest, as Pofciitilla fniticosa and small plants of
Quercus I'clutina. SoUdago rigida and S. neiiioralis occnr, but not in

sufficient numbers to produce the usual color-dominance. Other
prairie plants occur, but very little sod is being formed. Quercus
velutina seedlings develop readily.

List of the Species of the Sporobolus heteroIepis-Sorghastrum
nutans Coiisocies of the Bunch-grass Association

(Of the typical portion only)

Dominant Species

Sporobolus hcterolepis Andropogon scoparius

Sorgha^irum nutans Andropogon furcatus

Secondary Species

Panicuni virgatnni Aster ptannicoides

Solidago rigida Polygonum tenue

SoUdago nemoralis Anwrpha canescens

Spartina ntichan.riana Euphorbia, corollata

Koeleria cristata Solidago speciosa angustata

Relic Species

Sporobolus cryptandrus .'

Invading Species ;

Quercus velutina Lobelia spicata

Liatris scariosa Potrntilla arguta

Potentilla fruticosa Comandra umbellata

THE UATRIS SCARIOSA ASSOCIATION

Following the Artemisia-Panicuiu association or either ot the con-

socies of the bunch-grass association, is another association of xer-

ophytic plants, the Liatris scariosa association.

Location.—This association is found particularly upon the sand

ridges farther inland than the fringing dune. It is best developed to-

ward the southern part of the region, where it dominates the ridges

of nearly pure sand. Toward the northern parts of the region the

black oak has obtained dominance on the sand ridges, although the

Liatris scariosa association may remain coexistent with it, but occu-

pying the open spaces between the trees.

Physical Characteristics.—The soil occupied by this association

is essentially sand to which a little humus has been added, though not



302

in sufficient quantity to change the color. The ground is protected

from the lake by the fringing dune. The ridges, which parallel the

bluff, are low (1-5 dm.) and usually free from blowing, but occa-

sionally small blowouts are developed.

Ecological Characteristics.—The vegetation is essentially open,

and consists mostly of upright plants half a meter or more high. To-

ward the sides of the ridges, where the soil contains more humus,

are invaders of more typical prairie associations. The plants of this

association need a maximum of light and conseciuently do not long

withstand the shade of invading oaks. Yet the vegetation is rela-

tively so open that the IJatris scariosa association forms one of the

important pathways for the spreading of the oak woods. The sta-

tions of its best development are separated from the main body of the

oaks by the area of the pines. The latter has acted as a partial bar-

rier in retarding the development of the black oaks on the ridges be-

tween Waukegan and Beach.

The Association.—This association has been named from its most

imposing species, blazing star (Liatris scariosa). This plant, with its

large purplish spikes, is thoroughly dominant in the serotinal and au-

tumnal aspects. During the estival and early serotinal seasons the

white blossoms of flowering spurge {Buphorbia corollata) are almost

equally conspicuous. A few other species of less importance are

typically charcteristic of the association, such as Castilleja sessilitlora,

Liatris cylindracea, lead plant (Amorpha canescens), bush clover

{Lcspedeza capiiata), and black-eyed Susan (Rndbeckia hirta). In

addition to these, almost any sand-preferring plant may be found in

greater or less abundance in this association. The lines of succes-

sion leading from this association may proceed to any of the three

provinces represented in this region. In the northern part of the

region the succeeding association is usually the oak forest; in the vi-

cinity of Beach it may be the heath or, to a much smaller extent, the

pine woods ; and near Waukegan it is usually tlie prairie associations,

such as the Liatris spicata, each one of which will be described later.

LIST OF THE SPECIES OF THE LIATRIS SCARIOSA ASSOCIATION

Dominant Species

Liatris scariosa Oenothera rhomhipetala

Castilleja sessilitlora Lespedeza capitata

Euphorbia corollata

Secondary Species

Amorpha canescens Aster niidtiflorus

Aceratcs viridiHora Andropogon furcatus



303

Aster azureiis

Rudheckia hirta

Solidago nevi oralis

Panictim hiiacliucae (in blowing
sand

)

Tradcscantia reflexa

Liatris cylindracca

Relic Species

Koeleria cristata

Lithospennmn giiielini

Panicum z'irgattim

Calam oznlfa longifolia

Carex ttnibcllata

Potcntilla argiita

Asclepias ample.vicaiilis

SUcne aiifirrhina

Polygonum temic

Salix glaiicoji'iylla

Jiinciis halticits littoraUs

Cycloloiiia atriplicifoliiim

Andropogon scoparins

Relic species persisting in places in which this association develops

after oaks have been cleared off

Anemone cylindrica Smilacina stellata

Heliantliiis occidcntalis Hieracium canadensc
Lupinits pcrennis

Invading Species

Arctostaphylos uva-ursi

Junipcnts horizontalis

Befiila alba papyrifcra

Potcntilla fntticosa

Lobelia spicata

Linum virginianuui

Aster ptannicoidcs

Pctalostemuni candidum
Pctalostouiitn piirpureum

Couiandra uiiibcUata

Silphinni iiitcgrifoHuiii

Qiiercus vclutina

Rhus toxicodendron

Pragaria zirginiana

Asparagus officinalis ('ave\'ectant

under very small 0. vclutina)

Poa couipressa

THE POA COMPRESSA ASSOCIATION

The sand-plain which stretches inland from the limit of storm

wave-action, particularly from the state line to Kenosha, is char-

acterized by a light sod of English blue grass {Poa couipressa) rather

than by blazing star (Liatris scariosa) or black oak. Farther inland

this association may also occur on ridges from wliicii the black oaks

have been removed.
Physical Characteristics.—The ground on wliich tliis association

occurs is quite pure sand, made more or less yellowish by the admix-
ture of a substance which tends to cement the sand grains together.

Occasionally there are deposits of what a])pears to be guano, al-



304

though this region is no longer a breeding place for gulls. The sand-
plain is very flat, and slopes down away from the lake rather than to-

wards it. Ordinarily the sand is fixed; but when storm waves are

able to effect entrance, the sand is released and is usually blown into

the lake.

Ecological Characteristics.—A comparatively thin growth of grass

sufficiently dense to prevent blowing but not sufficiently dense to ob-

scure the yellowish color of the sand, is the prevailing feature of this

association. Secondary species occur here and there but are nowhere
of much importance, since they occur as scattered individuals among
the grass plants, wliich form about 90 per cent, of tlie area. Near the

lake the grass plants are separated two to three centimeters (see

foreground. Fig. i, PI. XLVI). On the ridges nearer the western

boundary, however, the grass plants grow much closer together and
form a true sod, which is usually effective in preventing further suc-

cession.

The Association.—The grass, Poa compressa, is the dominant spe-

cies and thoroughly characterizes the association. The secondary

species are, for the most part, merely sand plants which happen to be-

come established. Some of them are relics of the Quercus velutina

association in places where oaks have been removed, others are nor-

mal beach-plants, and several are weeds that grow readily in sandy

ground. Ecesis (establishment) is not difficult for the weeds, since

the ground is so open. A few species are indicative of successions.

Near the lake the presence of small plants of Jiimperm horisontalis and

/. coininunis dcprcssa look toward a heath, but in some other places

the dense growth of this grass has been responsible for the dying out

of the junipers. On the ridges farther inland the occasional pres-

ence of seedling trees indicates the approaching development of a

forest.

LIST OF THE SPECIES OF THE POA COMPRESSA ASSOCIATION

Dominant Species

Poa compressa

The most important secondary species near the lake shore

Monarda punctata Ccnchnis caroHnianns

Sporobohts cryptandrus

Other secondary species near the lake shore

Verbena hastata Achillea millefolium

Brigeron canadensis Anaphalis margaritacea



305

Verhascmu thapsus Draba caroliiiiana

Cacalia fuberosa Oxalis siricta {very smaM plants)

Panicum sp. ? Scutellaria parvida

Erigeron divarkatus Hypericum kaluiianuvi

Poa pratcnsis Potcntilla arguta

Ruuic.v acctoscUa Buphorhia corollata

Invading species living near the lake shore

Pycnantheuium virginianiiin Lobelia spicata

Juniperiis horizontalis Isanthus brachiatiis

Jitniperus communis depressa

Secondary species in the inland areas

Rudbeckia hirta Ambrosia artcinisiaefolia

Oenothera biennis Aster dnnwsus
Euphorbia corollata Heliantheuium majus
Koeleria crisfata Juncus tenuis

Verbascum thapsus O.valis stricta (dwarfed plants)

Achillea millefolirun Trifolimn repens

Erigeron annitus Panicum scribnerianmn

Erigeron canadensis Riimex crispus

Erigeron ramosus Solidago serotina

Cyperus HHcnlmis macilentns Euphorbia maculata

Poa pratensis Fragaria virginiana

Plantago major Cirsium arvense

Rume.r acetosella Digitaria sanguinalis

Lepidium apetahnn Desmodium illiuoeuse

Rosa humilis

Relic species in the inland areas

Juncus balticus littoralis Jnniperus communis depressa

Lithospermum gmelini Junipertis horis^ontalis

Invading species living in the inland areas

Lobelia spicata Monarda mollis

Potcntilla arguta Vitis vulpina

Verbena hastata Sambucus canadensis (small)

Solidago graminifolia Sali.v spp. (seedlings)

Allium cernuum (rare) Quercus velutina (seedlings)

Aster asureus Juglans nigra (seedlings)

Hclianthus grosseserratus Carya ovata (a few seedlings)

Prunella vulgaris ("much dwarfed) Crataegus punctata (a few seed-

lings)



306

THE ARCtOSTAPHYLOS-JUNIPERUS HEATH ASSOCIATION

Following Warming, a heath may be defined as an area of low,

evergreen vegetation. In Europe the heaths are composed mainly of

ericaceous plants. In this area, the vegetative structure is similar, but

the ericaceous plants play more of a secondary part.

Location.—The heath is best developed in the part of the region

near Beach, where it covers what has been a dune-complex. It is be-

coming well developed on the present dune-complex, which is shel-

tered by the pine forest. Thence the heath extends south behind the

bunch-grass until it disappears a little north of Waukegan. To-
wards the south its development is mostly in patches rather than a
general condition. North of Zion City the heath exists as relic

patches, of which there are but a few.

Physical Characteristics.-—The heath usually appears as sandy
ground almost entirely carpeted with low, shrubby, evergreen plants,

such as are in the foreground of Figure i, Plate LII. The color tone is

dark green, especially in the winter. The sand is somewhat darker

in color on account of the admixture with debris and humus materials.

Ecological Characteristics.—Invading heath plants are in ephar-

mony (close accord) with the ecological conditions which they en-

counter. Once they become established, however, they bring about
radical changes, the most important of which is the institution of hu-

mification rather than eremacausis. Blowing sand, leaves, and de-

bris are caught and held between the branches of the heaths. For this

reason, if nothing interferes, a heath is usually growing upward in

hight. Although the ground is carpeted, there is still sufficient room
for interstitials.

The Association.—In this area three species characterize the heath.

Juniperus horicontalis and bearberry (Arctostaphylos uva-nrsi) are

of prime importance, while Juniperus couiuiunis dcpressa is less so.

The first two are essentially mat-formers, while the /. communis dc-

pressa usually forms a table, elevated two to four decimeters above

the surroundings. J . horizontalis forms large mats by growing ra-

dially. The runners, as the branches may be termed, take root at in-

tervals. This results in a gradual movement of the whole plant. In

the larger mats the central area is dead, and in some instances has

given rise to blowouts. Often, however, the center may be occupied

by a normally developed plant of Juniperus comuiunis depressa. It

is evident that this came in last because of the dead stems of the J.

hori::ontalis which remain under it. A well-developed /. communis
depressa so excludes the light that no plants will germinate or

grow under it. The runners of the /. horizotitalis send up twigs



307

which bear the leaves. The leaves of the season are more or less

coated with a bloom which gives them a somewhat whitish a]>

pearance. The tips of the runners project into the air at an angle of

about 25° to 30°. Should blowing sand encounter them a small ridge

is built. Between these runners debris accumulates fairly rapidly, and
as it is not blown away during the winter it contributes to the en-

richment of the soil. Many seeds also are retained, and when proper

conditions are attained they grow. Some of them may replace the

heath altogether. This juniper, as well as the other two heath plants,

has seeds which are eaten by birds, although the birds seem to prefer

the bright red berries of Arctostaphylos. The latter plant, known as

the bearberry, is of second importance. What has been said about

Jimipents Jiorizontalis applies here almost ecpially well. The develop-

ment of the runners is not so noticeable, however, and a greater

amount of debris is retained in its denser network of branches.

The development of Jiiniperus coiiniiimis depressa reminds one very

strongly of the development of conifers near the tree line in Lapland
(Kihlman, 1890). The truncated top of this plant is characteristic

of all the individuals wherever they are growing. Some of these ta-

bles are a little over a meter in diameter. They var}' in hight from
about two decimeters up to nearly a meter. The explanation which
Kihlman found to solve the problem in Lapland has no bearing in

this case, however, for it seldom happens that there is sufficient snow-

in winter to cover even the lowest of these tables. The explanation

lies more probably in the fact that this growth is a germ character of

the species, for, in so far as evidence is at hand, edapliic factors

merely change the amount of growth and not its manner.

For northern Michigan, where the heath is much better repre-

sented than in this region, Whitford (1901:298) lists the character

plants as follows: Juniperus coinmimis, J. horizontalis, Arctostaph-

ylos uva-nrsi, bracken (Pteris aqnilina), Zygadeuus chloranthus,

Solidago ncinoralis, bluebell (Campanida rotiindifolia), and Coniaii-

dra niubellata. Of the eight species, five occur in the Beach area, and
four of these are important members of the heath association.

Secondary species in this association are not very numerous and
very few of them are typical of the association. They are either rel-

ics of past associations or invaders of succeeding ones. In no case do
they add to the general character of the vegetation, although they

may greatly change the appearance of individual parts.

The health plants come in on Calanwvilfa or Priinus puiiiiJa dunes,

which they work over into Juniperus dunes. In the meantime the

plants spread from the dime over the interdunal spaces. When these



308

become covered or nearly so, the dune-complex has been changed into

a heath. Blowouts occurring in the heath are, in general, revegetated

with heath plants rather than with invaders. This will be discussed

later, under the general topic of blowouts.

This association is a transitory one of northern affinities, and all

the evidence goes to show that it is very gradually being driven en-

tirely from the region. In the northern part of this area it has dis-

appeared already. In the central part north of Dead Lake the Qiier-

cus veliitina association is taking its place. For a little ways south

of Dead Lake it is being slowly replaced by pine trees. The only

places where the heath is reproducing itself are still farther south, al-

though at tlie same time the prairie is coming in from the westward
more rapidly to take its place.

LIST OF THE SPECIES OE THE HEATH ASSOCIATION

Dominant Species

Juniperus horizontalis

Arctostaphylos nva-nrsi

Secondary Species

Solidago ucm oralis

Relic Species

Andropogon scoparius

Calaiuoz'ilfa longifolia

Sali.v glaiicophylla

Koclcria cristata

Salix syrticola

Invading Species

Ceanofhiis ainericanns

Popiilus dcltoidcs (1.5 m. high)

Quercus vclutina

Potcntilla fruticosa

Aster pfaniiicoidcs

Panicnin virgatian

Popidiis candicans (0.6 m. high)

Liatris scariosa

Juniperus communis deprcssa

Juniperus virginiana (one plant)

Pctalosteuniui purpurenni f. are-

narium

Prumis piiniila

Artemisia caiidata

Junciis balticus littoralis

Sorgliastrum nutans

Finns strohns

Finns laricio

Pinus silvestris

Poa compressa

Hypericum kalinianimi

Aster azjirens

Tilia aniericana (one plant 0.5 m.
high)

THE PINE FOREST ASSOCIATION

General Location and History.—South of the Dead Lake there is

approximately a square mile of ground forested by coniferous trees,



309

forming the pine association. Its present extent is much less than
formerly. This is due to cutting, burning, erosion by the lake, and to

natural successions. Of the three species of conifers that form the

greater part of the association, only one is native to tlie region. This
species, Pinus strobus, was formerly relatively common, but is now
represented only by a few rather old trees in isolated situations. From
the taxonomic nature of the other three species, Pinus laricio and Pinus
sih'cstris and Pinus sp. ? it is evident that they have, at some past time,

been planted there by man. It has been difficult to secure accurate

evidence as to the date, but it was probably sixty or seventy years ago.

As long as the groves were taken care of the pines flourished ; but with
neglect and succession they are slowly disappearing.

Physical and Ecological Characteristics.—^The pine association

occurs on sandy soil and especially on tlie ridges of sand. Here, for

the first time, there is a definite differentiation between tlie soil and
the subsoil. Where the pines are densest there is a carpet of pine

needles, which are gradually being converted into htmius. The trees

afford plenty of protection for ground plants, but at the same time

cut off so much light that ground plants can only occur in the inter-

stices between the trees and in places where a tree has been removed
or cut, thus permitting more light to reach the ground. As a result

of the ground-covering, water is easily retained and conditions in gen-

eral are less xerophytic than those on the heath.

The Association.—-This association is a representative of the bo-

real element which has remained as a relic of the postglacial conifer-

ous forests which at one time were dominant in this region. In places

where the pines are dense, the association is more typical of its ap-

pearance in the northern regions. There are usually few or no sec-

ondary species in such situations. The exceptions are false Solomon's

seal (Sniilacina stellata), Anemone cylindrica, and Poa compressa.

The ground is carpeted with needles and pine cones. In places wliere

this association is more open, as along the ridges, there is an abund-

ance of secondary species, all of which represent succeeding associ-

ations. Which association does follow, is, of course, determined by
the number and nature of the secondary species. In the ridges to-

wards the southward, where the soil is more xerophytic, prairie

plants surround the pine trees and often occupy the groiuid clear up to

the trunk of the trees. (PI. LVI, Fig. 2.) In such places it is impossi-

ble for the pine to reproduce itself, as the seeds can not get down to the

ground on account of the tangle of prairie grass, debris, etc. ;\s long

as the pine trees live, they give the character to the area; when they

die, the prairie dominates entirely. Toward the northward, although



&

310

there are many prairie species around the trees, there are plenty of

young oaks, Quercns velutina, in all stages of development. They
grow quite easily and are able to replace the pine—not merely to dom-
inate the region with the dying of the pines as is the case with the

prairie plants. In the openings in the denser parts of the pine area,

the pioneer species that come in are forerunners of both the prairie

and the oak forest. Seedling oaks are rather plentiful and occur at

various distances from the parent trees, from which acorns were
probably carried and stored by birds, especially crows and blue jays.

If the oaks are present in any number they determine which succes-

sion is to take place.

Pinus strobits occurs rather commonly throughout the association,

but it is rather more abundant in the more xerophytic and less fertile

soils. It acts as a pioneer for this association, and even now is very

gradually reprodiicing itself on the edges of the prairie and marshes

or in broken places in the prairie. This, however, is taking place

much more slowly than the occupation of the pine land by oaks. The
densest growth of pine is formed largely of Pinus laricio and Pinus

silvestris, growing in separate groves.

LIST OF THE SPECIES OF THE PINE FOREST ASSOCIATION

Dominant Species

Pinus strobns Pinus sp. ?

Pinus laricio Larix dccidua

Pinus sihesfris

Secondary Species

Smilacina stellata Polygonatum conunntatuni

Oenothera rhonibipetala Aster azureus

Anemone cylindrica

Relic species which are very abundant

Junipcrus communis dcpressa Solidacjo ncni oralis

Juniperus horizontalis Buphorhia corollata

Arctostaphylos uva-ursi Lithospermum gmclini

Relic species which are not abundant

Elynius canadensis Artemisia candata

Aster dumosns Salix syrticola

Primus pnmila Arabis lyrata

Salix glaucophylla Sorghastruni nutans

Juncus balticus littoralis CaJanioi'ilfa longifolia

Panicum virgatiim Kocleria cristata



311

Invading species from the

Liatris scariosa

Potcntilla fruticosa

Poa conipressa

Poa pratcnsis

Trifoliuin hybridum
Plantago major
Pycnauthcimnn virginiamtm
Tara.vacimi crythrospcriiiuiii

Lobelia spicata

Satureja glabra

Invading species from the

Helianthemiim majus
Fragaria virginiana

Ritbus occidcntalis

Verbascum thapsiis

Ruiiie.v acetosella

Qucrctis vclutina

Salix spp.

Asparagus officinalis

Solidago serotina

Lonicera dioica

prairie and prairie-hke associations

Zizia aurca

Hypo.vis hirsuta

Sisyrinchium sp. ?

Phlox pilosa

Castillcja scssiliffora

Tradcscantia reffe.va

Comandra uiubcUata

Ccanothus ovatus

Bpilobium dcusuui

Bquisctuut laevigatnm

oak forest

Vitis vulpina

Maianthciii uni canadcnse

Lunula caiupcstris uiultiffora

Helianthus occidcntalis i. illinocn-

sis

Ceanothus auicricanus

Gcraniuvi carolinianuni

Lactuca canadensis

Rosa hnmilis

Pedicidaris canadensis

. THE QUERCUS VELUTINA ASSOCIATION

As the climax stage of the successions on the ridges of the sand-

plain, this forest association exists. The association obtains its start

in either of the prairie or coniferous types of vegetation, quite often

in broken places in them. It can obtain a slight foothold upon open

sand, but more usually the young oaks obtain their foothold in the

humus of the prairie or the pines. Development then is quite certain.

It is rather more rapid in the prairie situations. As development pro-

ceeds the prairie gives way. After a time the ground begins to be

more open as the ground-carpet disintegrates to a greater or less ex-

tent.. Thereupon eremacausis, at least with respect to the upper layers

of ground, begins again to be the usual state of affairs. This, coupled

with the winds of the more violent storms, causes the surface to

reassume a sandy appearance. The sand itself is more or less easily

blown, especially where the removal of any of the trees permits a

more o])en exposure. Such blowing results in the formation of what
are known as blowouts. While the upper layers may be sandy and
the secondary vegetation that of true sand ridges, in which there lias



312

been no intervening prairie stage, the subsoil in which the oaks are

rooted is distinctly humic in nature. The secondary species, how-
ever, consist of both prairie and sand plants, some of the latter of

which, as Juncus balticiis littoralis, may have persisted through the

prairie stage. The same thing happens with respect to the heath. As
soon as the oak becomes dominant, by its foliage, light is cut off from
the heath plants, and consequently the heath is gradually replaced.

Witli the disappearance of the heath plants the sand is left exposed to

blowing. In such situations blowouts are very common. The in-

vasion of the pines takes place much slower because that necessitates

the dying of the old pine trees. The oaks can not drive these out as

they can the herbaceous vegetation. The young pines can not germi-

nate or develop under the shade of the oaks, which results in the ex-

tinction of the pines by the dying of the old trees. As soon as a pine

dies, young oaks spring up in its place. They could not do this be-

fore on account of the great shade from the pine. Once sufficient

light is allowed, the oaks very rapidly replace the spot with trees,

against which invasion, in tliis region, the pines can do nothing.

The Liatris scariosa association may develop contemporaneously

with the Quercus velutina, but usually Liatris scariosa develops first,

and as it is a fairly open association the Quercus velutina c[uite read-

ily invades it. It retains nearly all of its identity, however, even after

invasion, because there is not as yet sufficient food material to support

a dense growth of oak. As soon as the oak does become dense, the

Liatris scariosa gives way.

In its primary stages the Quercus velutina association occupies

stable sandy soil where humification is the rule. The humus, however,

is not abundant, and consequently a luxuriant undergrowth is not de-

veloped. Protection against wind and sun is afforded, resulting in a

flora somewhat mesophytic in tendency, but the succession of this

association to a distinctly mesophytic one requires a space of very

many years. In the mature stages of the development of this asso-

ciation humification is very slow and may be absent. The oaks them-

selves are well developed but their shade keeps out sand plants which

would make a dense ground covering, while there is not sufficient

food material in the soil to permit the growth of mesophytic forms

which require the amount of shade that the oaks furnish. For these

reasons eremacausis again takes hold and very materially increases

the length of time between this association and the one that will

finally succeed it.

Because of its great diversity of environments this association has

a large number of secondary species, many of which belong more
properly to the associations which the black oak has displaced. The



313

association is characterized by the black oak, Quercus vclntina, which

is the only dominant species of this association in this region. Other

trees are virtually never present. Occasionally a few Piniis strohus

do remain as relics, and a few trees of Querats macrocarpa and Q.

alba occupy a mound north of Winthrop Harbor.

The Quercus vehttina association, as it is found in the Beach re-

gion, accords in all essential particulars with Jennings's associations

of the same name on Cedar Point, Ohio, and Presque Isle, Pennsyl-

vania (1908 and 1909). The same association occurs throughout

Illinois and southern Wisconsin in glaciated land which is xerophytic

in nature. In different parts of its range other species of oak also

may become dominant, as, for example, Quercus marilandica in Mason
County, but Quercus veluflna usually predominates.

LIST OF THE SPECIES OF THE QUERCUS VEEUTINA ASSOCIATION

Dominant Species

Quercus velutina

Secondary species which

Achillea ruillefoliuni

Amorpha canescens

Anemone cyUndrica

Aralia nudicaulis

Arabis lyrata

Asclepias tuberosa

Asparagus officinalis

Aster azurens

Aster scriceus

Baptisia leucantha

Ccanothus auiericanus

Cclastrus scandcus

Coreopsis lanceolata

Coreopsis pahnata
Desniodiuui illinoensc

Brigeron raiuosus

Euphorbia corollata

Fragaria virginiana

Gerardia grandiHora

Gerardia pedicularis

Hcliantheniuin niajus

Helianthus divaricatus

Helianthus occidentalis

are most characteristic

Lcchca leggettii

Lnpiniis perennis

Lepachys pinnata

Lu::ula cainpestris multiflora

Monarda fisttdosa

Monarda sp. ?

Mosses (unidentified)

Paniciim scribncriammi
Pedicularis canadensis

Physalis virginiana

Polygonatuui couiniutafutn

Potentilia arguta

Rhus toxicodendron

Rosa humilis

Rndbeckia hirta

Scrophularia leporella

Scutellaria parvula

Silene antirrhina

Silene stellata

Sniilacina stellata

S(didago arguta

Solidago serotina

Taraxacum erythrospermmn



314

Helianthus occidentalis f. illi-

noensis

Heliantliiis strumosits

Heuchera hispida

Lactuca canadensis

Tradcscantia rcflexa

Maiauthcimtin canadcnse

J'crbasciim tliapsus

Vitis vulpina

Zisia aiirea

Relic species which are most abundant

Arctostaphylos uva-tirsi

Juniperus communis depressa
Junipenis horij:;ontalis

Koeleria cristata

Lcspedcza capitata

Liatris scariosa

Secondary species which

Antennaria sp. ?

Arcnaria stricta

Asclepias syriaca

Aster novae-angliae

Carex bcbbii

Chenopodimn album
Convok'nliis sepinm
Bquisetuui arvcnse

Erigcroii canadensis

Hypericum sp. ?

Plantago major
Poa pratensis

Polygala sanguinea

ReHc species which are less

Acerates viridiflora

Andropogon furcatus

Andropogon scoparius

Artemisia caiidata

Asclepias incarnata

Aster dumosits

Aster ptarmicoides

Betula alba papyrifcra

Calamoz'ilfa longifoHa

Carex muhlenbergii

Ccanothns ovatns

Comandra nmbellafa

Bryngimn yuccifolium

Lithospcrmum gmelini

Oenothera rhombipetala

Panicum virgatum
Panicum spp.

Poa compressa

Solidago ncni oralis

are less characteristic

Polygala verticillata

Prenanthes alba

Pteris aquilina (rare)

Rosa blanda

Sambucus canadensis

Silphinm intcgrifoHum

Sisymbrium otHcinale leiocarpum

Smilax hispida

Solanum nigrum
Solidago canadensis

Stipa spartca

Trifolium repens

J'ibiirniim Icntago

abundant

Lobelia spica fa

Oxypolis rigidior

Pctalostemum candidum
Pctalostcmum purpurcum
Pinus strobus

Popidus deltoides

Popuhis tremuloides

Pninus scrotina

Pycnanthemuin z'irginianum

Rynchospora capillacea leviseta

Salix glaitcophylla

Salix longifoHa

Salix pediccllaris



315

Eupatorium purpiircuiii iiiaciilatiiin Sali.v spp.

Hypericum kaliiiianiun Sclcria trigloincrata

Juncus halticus littoralis Solidago graininifolia

Liatris spicata Spiraea salicifolia

Invading species, none of which are abundant

Allium cernuum Riidbeckia siihtoiiiciilosa

Amphicarpa monoica Smila.v ecirrhata

Aster macrophylhis Saiiiciila marilaiidica

Geranium carolinianum In burns :

Nepeta cataria Apoeynum androsaemifolium
Polygonum persicaria EpUobium angustifoUum
Prunella vulgaris Hclianthus grosseserratiis

Qucrcus alba (very few) Populus deltoides

Qucrcus macrocarpa (few) Populus tremuloides

Species whose occurrence is accidental

Apios tuberosa Cyperus rivularis

Catalpa speciosa (planted) Krigia amplexicaulis

Cirsium arrense

THE BLOWOUT ASSOCIATIONS

Blowouts are open sandy places evacuated by the wind. They
may occur in almost any of the associations that inhabit sandy ground.

They are usually started during the winter when the ground is not

well protected by vegetation. Once begun, however, any wind with

sufficient power to move sand may effect their greater development.

As a rule, in this region vegetation is more than able to keep pace

with any blowing that may take place, and so there is but little blow-

out development during the growing season. Blowouts are especially

liable to occur in the sand ridges, no matter whether these are ten-

anted by the heath, the Liatris scariosa, or the Qucrcus vclutina asso-

ciation. The blowouts of greatest extent occur in the Querctts velto-

tina association, more especially where trees have been removed.
This is because the shade from the oaks has reduced the density of

tlie vegetation underneath them and left more ground exposed to

the wind.

In general, the blowouts are elli])tic to oval in shape with their

major a.xis north-northeast or north-northwest. Occasionally a cir-

cular blowout may be found and less frequently crescent-shaped ones.

Winds from all directions of the compass are responsible for blow-
outs of greater or less extent, but the largest ones are formed by



316

either the northwest or the southwest winds, either one of which is

quite likely to be strong.

In some regions the flora of even quite widely separated blow-

outs is remarkably uniform, but this can hardly be said to be true

of this region. The blowout is in some measure dependent upon the

surrounding associations for most of its species, but there are a few
characteristic blowout species which do not occur in associations im-

mediately adjoining the blowout; as, for example, green milkweed
(Acerates z'iridiflora lanccolata), flowering spurge (Biiflwrbia carol-

lata), Cyperiis Hlicuhnis macilcntus, Sf^oroboliis cryptandrus, Oeno-
thera rhombipetala, Cyperus schiveinitcii, Corispcriiiuiu hyssopifoliimi,

and horsemint {Moiiarda puiictafa) .Though blowouts occur in sev-

eral associations, the association that succeeds the blowout need not

be the same as the one in which it started. Blowouts occurring in

the Qitcrctts z'elutina association sooner or later give place to Quercits

vehitina, often by passing through a heath stage. Blowouts occur-

ring in the heaths may become tenanted by one of several associations :

the Qucrcus vcliitiiia, a thicket, the Liatris scariosa, or the L. spicata

association. Blowouts in L. scariosa may become occupied by Oiier-

ciis Z'clutiiia, hut more frequently by Liatris spicata; or, occasionally,

by some of the marsh associations, if the blowing should continue

during the winter until the bottom of the blowout is below the water-

table level. Typical blowouts do not occur in Liatris spicata, but

occasionally, where the surface-covering of vegetation has been re-

moved by man, blowing ensues. Such blowing does not last long be-

cause tlie sandy bottom is usually damp, and am association such as

the Carex ocdcri ptiinila soon obtauis dominance and finally reverts to

Liatris spicata. Some of these difi^erent types of blowouts are shown
in Figure 2, Plate LI, Figure 2, Plate LII, and Figure i, Plate LIII.

Physically a blowout may be divided into four parts. The low

central part, or basin, is occupied by the basin association of deep-

rooted perennials, such as Acerates z'iridiflora laiiceolata. The wind-

ward slope, located on the side from which the sand is being blown,

is, with very few exceptions, occupied by the plants of tlie associa-

tion in which the blowout occurs. In the prairie blowouts, the wind-

ward slope association is characterized by a species of Panicuin, P.

huachucae, a feature which is markedly characteristic of the blowouts

at Hanover Station, Jo Daviess County, Illinois (Gleason 1910:79).

There, however, a different species, Pamcimi pseudopubescens, is

involved. The lee slope, which is directly across from the windward

slope, consists of constantly shifting sand, in which the blowsand as-

sociation of annuals usually dominates. The lee slope usually ter-



317

minates in a small dunelike ridge, termed the lee deposits, consisting

of the sand blown out from the basin. The dunelike form is main-
tained by sand-binding perennials, many of which are the dune-form-
ers on the lake beach.

Normally ven,- little blowing occurs during the summer, and most
of the blowouts show various stages of stabilization. This is most
frequently indicated by bush clover (Lespedcsa capitata), evening
primrose {Oenothera rhoinbipctala), and Panicum zirgatuiu, although
in any single blowout several other species may play the same role.

With the dying down of the vegetation in the fall, much sand is left

exposed to the winter winds, whose blowing power is not usually
much hampered by the protection of a snow covering.

LIST OF THE SPECIES OF THE BLOWOUT ASSOCIATIONS

I. Species characteristic of the basin association

Accra fcs firidiflora lanceolata Litliospernniiii angiistifoliuni

Sporobolits crypfaiidrus Lithosperuuim gmelini

Eiiplwrbia coroUata Rhus toxicodendron

II. Other species found in the basin

Cypcrus filicuhnis macilentus Jiiiiipcnix hori::ontalis

Oenothera rhoinbipctala Junipcnis conuniinis deprcssa

Koeleria cristata Opuntia rafincsqitii

Carcx niuhlenbcrgii Anwrpha caucsccns

Quercus z'chttina (seedlings) Junciis forreyi

Solidago nenioralis Rudheckia hirta

Arctostaph\los ui'a-ursi Hypericum Icalniiauuni

Smilacina stcllata Salix gUnicopliylla

Silcne antirrhina Aster ptarmicoides

Andropogon scoparius Liatris sp^icata

SciitcUaria parruhi Blcocharis intermedia

Liatris scariosa Lobelia kalniii

Tradcscantia rcflexa Potentilla fruticosa
'

Juncus balticus littoralis Polytrichum juniperinmn

Rosa huniilis J'erbascuni tluipsus

III. Species characteristic of the win<lwarfl sIo]ie

Panicum huachucae

The other windward slope species are the normal species of the

associations in which the blowouts occur, and consecjuently are not

listed.



318

IV. Species characteristic of the lee slope (blowsand associa-

tion)

Calcilc cdcntula

Pcstnca octoflora

Euphorbia polygomfolia
Sporoholus 'cryptandrus

Cycloloina afriplicifolium

Cypcnis Pliciilniis maciloifiis

Cypenis schwcinitsii

Corispcnniiin hyssopifoliuiii

Monarda punctata

Artemisia caudata

Cciichrus caroliniauus

V. Species characteristic of

Panicuin virgatuiu

Oenothera rhouihipetala

Lespedeza capitata

A rctostaphylos nva-ursi*

Tradcscantia retJcxa

Jttnipcrus horiconfalis*

Juniperus counuuiti-s depressa*

the lee deposits

Popidns dcltoides

Asclepias tuberosa

Poa compressa

Prunns pumila
Calaiuoz'ilfa louyifolia

Elyuius cauadeusis

Buphorhia coroUata

VI. Miscellaneous species occasionally occurring in blowouts

Chenopodium album
Solidago serotina

Arenaria stricta

Mclilotus alba

Hieracium canadeusc

Aspidium thelypteris

Rynchospora capillacca lexiscta

Linum sp. ?

Saturcja glabra

Aster asurens

Pycnanthemum virginianum

Trifoliiim repeus

Solidago oliioensis

Orobanche fascicidata (par-

asitic on Artemisia^

The Associations of the Marsh Habitats

In the low ground back of the fringing dune and south of Beach

are two small bodies of water known as the Dead River and the Lit-

tle Dead River. The former expands in width as it nears Lake
Michigan and becomes what is know as Dead Lake. The small

drainage area commanded by these rivers is very level, and conse-

quently there is very little flow of water. For the greater part of

the year the outlets into Lake Michigan are closed by a ridge of sand.

The surplus water, at these times, is partly evaporated away, partly

sinks through the sand to the lake-level, and is partly taken up by
the plants which grow along the shores. In general physical charac-

*The asterisk denotes tliat the species spreads in from surrounding areas by
vegetative growth.

,



319

teristics these situations are quite similar to lake beaches. The im-

portant difference is the slow movement of the water in the rivers,

which are not sufficiently extensive to permit the wind to raise waves
which could destroy the vegetation along the shores. The bottom of

these rivers is seldom more than one or two meters below the level

of Lake Michigan.

The associations which occur in these localities are characterized

by the great abundance of a very few species. The associations are

restricted to narrow bands which spread out horizontally for many
meters. This giA-es rise to zones of associations around the ponds
and along the streams. The associations may alternate to a limited

extent. They are, however, sharply separated from one another by
definite tension lines, which are sharpest between the associations

farthest out in the water. Landward the tension lines are occu-

pied by species of both of the bordering associations and in many
cases by small plants which occur there only.

THE PI,.\NKTON ASSOCI.\TlON

The free-swimming protozoans and algae which enter into the

plankton were not investigated, owing to lack of proper facilities

for such work.

THE CH.\R.\ .\SS0CI.\TI0N

The bottom of the deeper parts of lakes and ponds in northern

Illinois and Lidiana is usually covered with an alga, Chara, con-

stituting the Chara association. There are no secondary species with

the Chara, as it normally occurs in this area. In streams with vis-

ibly running water there is no Chara. The accumulation of Chara
furnishes a lodging place for the seeds of Potaiiiogefon, giving rise

to the following association.

THE POTAMOGETON ASSOCIATION

This association occurs in both quiet and running water, al-

though usually with different dominant si>ecies in the two cases. The
association consists mainly of plants that are entirely submerged,

although some of them may mature their flowers and fruit at the

surface of the water. This association frequently starts near the

edge of the Chara, or it just as frequently has its beginning in ponds

in which there is no Chara. \n the main part of Dead Lake the as-

sociation is characterized l)v a single sjiecies, Potamogcton natans.

In some of the ponds, where the water is not so deep, it may have



320

associated with it Myriophylluiii vcrticillatuiii. In little streams of

running water the dominant species is usually Potamogeton foliosus

niagarensis, and associated with it are Myriophylluin vcrticillatum and
Blodea canadensis. In one such little stream Myriophyllum and Elodea
occur almost to the exclusion of the Potamogeton. This association

is developed to such a limited extent that in a description of this

region no adequate idea can be given of it. A more detailed account

may be found in Jennings (1909).

THE CASTALIA-NYMPHAEA ASSOCIATION

In shallower water than that occupied by the Potamogetons is

the Castalia-Nymphaca association. The water is quiet and a layer

of mud covers the bottom. The plants of this association are essen-

tiall_y submerged, but they frequently have their leaves at or above

the surface of the water. They may mature their flowers and fruits

under water, at the surface, or above the water. This association is

very effective in accumulating matter which builds up the bottom.

This work is furthered not only by the petioles of the water-lilies,

which serve to catch materials, but also by the semi-floating secondary

species when they occur. The large leaves of the water-lilies, spreading

out on the surface, serve to keep the water calm, and this pemiits a

deposition of the matter brought there in suspension. The very

noticeable accumulation of organic matter on the bottom is correlated

with slow subaqueous oxidation.

The Association.—This association is not well represented in the

area. In only one pond do both the species which give the name
to the association occur. When this happens, the white water-lily

(Castalia tuberosa) appears to prefer deeper water than the yellow

water-lily (N'yniplwea adz'cna). Castalia is not usually emersed,

while Nyinphaca frequently grows above the water. In this particu-

lar pond, associated with the water-lilies are Ccrafophyllinn deiner-

sinu, Chara, Potamogeton sp. ?, and Elodea canadensis. In all the

other places in this region where this association occurs, it is repre-

sented by the dominant species, Nyinphaea adven-a, and there are

.seldom any secondary species with it. (See PI. LIU, Fig. 2.) Not
only does Nympliaea occur along the ponds in the swales, but

it also grows in a good many of the ditches and holes that have

been dug in the right of way of the Chicago and North Western rail-

way. Only one case is at hand to give an idea of how long it takes

for the NympJiaea to appear in a ditch after it has been dug. In an

excavation made during the summer of 1906 NympJiaea appeared in



321

the permanently standing water during the season of 1909. Its nearest

possible source was about forty meters away, and the probable agent

in dispersal was a marsh bird. Occurring with Nyiiiphaca in some of

these artificial situations, as well as in natural ones, were Polygonum
amphibktm liartzvrightii and Sparganinm eurycarpnm, which more
properly belong to other associations. In areas in the western part

of Lake County, Illinois, this association is often dominated during

the fall by the tall stems of Pontcderia cordata, but until three exam-
ples of it were found during the summer of 1910, this plant was what
Harper (1906:329) has termed a "notable absentee."

LIST OF THE SPECIES OE THE CASTALIA-NYMPHAEA ASSOCIATION

Dominant Species

Castalia tiibcrosa Nymphaea advena

Secondar}' Species

Pontcderia cordata Potamogctcn spp.

Ccratophylluui deincrsiim Elodea canadensis

Potamogetoii )iafa)is

Relic Species

Chara sp.

Species of accidental occurrence

Polygonum avipliibinin liarturiglitii Sparganinm eurycarpnm

THE RANUNCULUS AQUATILIS CAPILLACEUS ASSOCIATION

After the establishment of the NynipJwea association around the

margin of many of these ditch pools, plants of Ramincnhis aqnatilis

capillacens appear at the lower (inner) edge of the Nymphaea.
Thence they spread out, and in time usually cover the surface of the

open water. The vegetation iloats out towards the center of the

water, while the roots remain in the Nymphaea. The mass of Ranun-
culus becomes so dense in some of the smaller pools that it can sup-

port the weight of marsh birds. The flowers of this plant are

borne two or three centimeters above the water on slender hollow

stems. While the plant is in bloom the pool appears almost white.

With the R. aquatilis capillacens are occasionally a few plants of R. del-

phinifolius, and mixed in with the leaves are colonies of Lemna minor.

This association is one of the many small associations of water-

plants which are rather local in their distribution even in a given

area. Ultimately it will be displaced by the Castalia-Nymphaea as-

sociation.



322

THE LEMNA-RICCIA ASSOCIATION

An alternating association with the one just described is the

Leiiina-Rkcia association. It shows a tendency to inhabit the

longer, narrower pools, where there is less chance of the wind dis-

turbing the water. The plants differ from those of the Ranunculus

association in that they are free-floating. They mass together, how-
ever, in great mats which cover the surface of the water with vege-

tation. Lciiina seems to prefer the more open water, while Riccia

shows a tendency to remain nearer the border association of Nym-
phaca or TypJia. The Lciinia and the Riccia are, however, so inter-

mingled with one another that they have essentially the same ecologi-

cal conditions to meet, and so are parts of the same association.

This association can only exist as such in quiet water, for in streams

the plants are washed away. On this account it is more conspicuous

in the small pools, although careful search usually revealed its plants,

especially the Lciiina^ among the grasses or sedges that form the

bordering amphibious vegetation of the rivers. Numerous small

animal forms are associated with these plants, but no other species

of plants have been observed with it in this region.

THE MENYANTHES-SAGITTARIA ASSOCIATION

In fairly wide and shallow (2-4 dm.) sloughs the Castalia-

Nyinpliaca association occupies the central part, where there is a lit-

tle running water, especially during the spring floods. Bordering it

on either side is the expanse of the Menyanthcs-Sagittaria associa-

tion, wdiich reaches to the sedges. As it occurs in a few of the

situations it is a typical bog, like those so much more common
farther north. The bottom is very level and somewhat peaty. The

plants of this association have their root systems entirely submerged,

while the leaves and the flowers are usually above the surface of the

water. The vegetation is very dense, as shown in the center of Fig-

ure 2, Plate LIII.

Arrowleaf (Sagittaria latifolia) is always one of the dominant

species in the bogs that occur in this region. It occurs along streams

of running water as well, and associated with it are many of the

same secondary species that accompany it in the typical bog situation.

This association is boreal in distribution. Here, near its southern

limit, as shown in Transeau's map of the distribution of bog plants

(1903:406), it is not typically developed. The species that is most

abundant in this association in this region, Sagittaria latifolia, is not

listed by Transeau as a bog plant because it is not characteristically



323

of this habitat and its range is much wider than that of bogs. Never-
theless, in all the bogs of this region it is one of tlie dominant
species and occupies from thirty to sixty per cent, of the area of the

association. The two species that complete the list of the dominant

species are given in Transeau's list of the plants characteristic of

bogs across northern North America (1903:405). Of the two,

buckbean {Mcnyantbcs trifoluifa) is the more abundant, and may
form as much as fifty per cent, of the vegetation in some of the

bogs, while PoientUla palustris is relatively infrequent. Secondary
species are not common because the Sag'ttaria and the Mcnyanthes
so occupy the area that very little interstitial room remains. Those
that occur most abundantly are bladderwort ( Utriciilaria vulgaris

americana), Polygonum amphibvim hartivnghtii^ Lysiiiiacliia thyrsi-

flora, Acorns calamus, and Proserpinaca palustris. Towards the

edge, an invader of the sedge association, Carcx lajiugiuosa, may be

within the limits of the association. In less typical situations, es-

pecially those near the railway, where the drainage has been inter-

fered with, there are mixtures of this association with species of

others near by, the result of which is vegetation of the following

composition: Mciiyanlhcs trifoliafa, Sagitfaria latifolia, Utricularia

vulgaris americana, Scutellaria galcriculata, Hypericum I'irginicum,

Bidens trichospcrma tenuiloha^ Iris z'crsicolor, Lysimachia tliyrsi-

ffora and Polygonum muhlcnhergii. In other situations, differing from
these, were Acorns calamus, Alisma plantago-aqiiatica, Oxypolis
rigidior, Asclcpias incarnata, Polygonum hydropiperoides, and Lnd-
vigia palustris in addition to the dominant species.

Along some of the ditches in the right of way of the Chicago and

North Western railway this association is appearing. In most of them
the first member to appear is Mcnyanthes. With it are associated

Utricularia vulgaris aniericana and Proserpinaca palustris. In one
case Menyanthes and Proserpinaca were giving way to Spartina and
Cephalanthiis, which is worthy of mention because the two bushes

of buttonbush that occur in this station are the only individuals in

this region of a species so characteristic of similar situations in other

places. Sagittaria will not as a rule come into these ditches until

they are larger in size, and not e\'en then unless there is some move-
ment in the water.

Along the little streams that lead from the bluff towards Lake
Michigan, the Menyanthcs-Sagittavia association is usually repre-

sented by Sagittaria alone. With it may occur a few secondary

species, as Oxypolis rigidior, Cyperus Huviatilis, Alisma plantago-

aquatica, Proserpinaca palustris, Veronica anagallis-aquatica , Ranun-
culus delphinifolius, Scirpus atrovirens and Pcnthorum sedoides.



324

The dense growth of this association aids veiy materially in

building- up the sloughs, after which it is replaced by other associa-

tions that would otherwise have been unable to develop.

LIST OF THE SPECIES OF THE MENYANTHES-SAGITTARIA ASSOCIATION

Dominant Species

Menyanthcs trifoliaia

Sagittaria latifolia

Secondai-y Species

Utricitlaria vulgaris americana

Polygonum amphibium
hartzvrightii

Lysiinachia thy rsiflora

Acorus calauiits

Proserpinaca palustris

Polygonum viuhlcnbergil

Relic Species

Nymphaca advcna

Invading species

Carex lanuginosa

Hypericuui z'irgijiiciim

Bidens frichospcriua tenuiloba

Iris versicolor

Asclcpias incarnata

Potentilla palustris

Scutellaria galcriculata

Alisuia plantago-aquatica

Oxypolis rigidior

Polygonum hydropiperoides
Ludzngia palustris

Sagittaria heterophylla rigida

J'^cronica anagallis-aqnatica

Ranunculus delphinifalius

Scirpus duviatilis

Scirpus atrovirens

Sport ilia michaud-iana

Cephalanthus occidentalis

Pcnthontm sedoides

THE CAREX ASSOCIATION

In the bogs, above the Menyanthes-Sagittaria association, occurs

a sedge association composed almost entirely of species of Carex.

The sedges grow quite densely, and while above the surface of the

water the cuhns seem to be regularly distributed, beneath the surface

they are found to be grouped together in bunches or hummocks. If the

water-level is lowered, this gives rise to the hummocks, which are

so characteristic of boggy shores. The bottom is decidedly muddy,
and the water is shallower than in the two preceding associations.

The sedges afford good hiding places for several of the marsh birds

and other animals.

There are seldom any secondary species with the sedges. In

the bogs, Utricnlaria ziilgaris americana and Iris versicolor have



325

been found as secondary species in several stations, and, in addition

cardinal-flower (Lobelia cardinalis) in a single station. In a few
of the ditches along the railway, where this association has found its

way, Spartina viichauxiana, Lobelia cardinalis, and a few plants of

Iris versicolor take the part of secondary species. Dulicliitiin arimdi-

naceum, a typical bog plant, is present in this region in only two
very small boggy places in the midst of a succeeding Populus-Salix-
Coniiis thicket, where it was accompanied by Carcx sp.

Along the shores of Dead Lake, except for a few places where
the Castalia-Nymphaca association exists, this association of sedges

forms the outermost zone of vegetation visible above the water. At
the outer edge it is formed solely of two species of Carcx—Carex
lanuginosa, and the other was probably Carcx filiforinis, although

none of its flowering culms were obtained. Nearer the shore are

invaders of associations occupying shallower water. Among these

invaders is Scirpiis zvlidus, which may, in other lakes, grow in much
deeper water than the Carex does in the Dead Lake. This leads to

the conclusion that, although most of the acjuatic and semiaquatic

plants are closely restricted within certain depths of water, their

position in any given locality is determined by competition of asso-

ciations rather than by the different physical requirements of the

plants. The same relative arrangement is maintained within the

limits of the requirements of the individual plants in different locali-

ties, even though the absolute conditions may vary greatly.

LIST OF THE SPECIES OF THE CAREX ASSOCIATION

Dominant Species

Carex filiforinis Carex stipata

Carex lanuginosa Carex buxbawnii
Carex stricta Carex spp.

Carex coinosa Dulichiuiu ariindinaccuiu

Carex riparia

Secondary Species

Utricularia x'ulgaris aiiicricaua Acorns calajuns

Lobelia cardinalis Bchinochloa crusgalli

Spartina michauxiana

Invading Species

Iris versicolor Typlia latifoUa

Scirpus validus



326

THE PHRAGMITES-TYPHA ASSOCIATION

In sliallower water than the Carex association is the Phragmites-

Tvplia association. Ecological conditions seem to be much the same

as for the Carc.v except that the water is shallower. The plants of

this association are rooted in muddy soil a few decimeters below the

water-level and have their vegetative parts comparatively high in the

air, where they are exposed to the dicing effects of the wind and sun.

The cattail (Typha) is, in a small measure, adapted to these condi-

tions by having its broad leaves edgewise with the noonday sun.

Adaptation would seem hardly necessary since the plants can obtain

water as fast as it is evaporated. Even on the hottest and driest days,

Typha never appears wilted, but Phraguiitcs may be quite noticeably

wilted. Each of the dominant species dominates the situations in

which it is located. Very dense plant families are formed on ac-

count of the close method of vegetative reproduction. Although

these two species seldom intermingle, they conform exactly to the

limits of water-depth in which either will grow. For these reasons,

either may be farther out or nearer the shore, or a family of one may
be between two families of the other, and this without change of wa-

ter-depth. There is very little room for secondary species, and tlie

few that do occur are relics or invaders of other associations. When
this association appears in the ditches along the railway, the dominant

species is usually Typha on account of the much greater production of

its seeds. In two pools Typha angustifolia alternates with T. lati-

folia. Hybrids between these two species occasionally occur, and

there is a form having two completely separated spikes of pistillate

flowers in addition to the staminate spike.

LIST OF THE SPECIES OE THE PHRAGMITES-TYPHA ASSOCIATION

Dominant Species
*

Typha latifolia Typha angustifolia

Phragmites com in iinis

Secondary Species

Acorns calamus (a very little) Oxypolis rigidior

Ufricularia I'ulgaris anicricaua Scirpus afroi'ircns

Scirpus rubrotiuctus

Relic Species

Carex lanuginosa (a. little) Proscrpinaca palustris

Invading Species

Scirpus validus



327

The follow ing floating plants are frequently present

:

Riccia fliiifans Lciinia muior

THE SCIRPUS VALIDUS ASSOCIATION

In still shallower water than the preceding association occurs the

Scirpus validns association. It is characterized by the bulrush, Scir-

pits validns, and the very closely related species, 5". hetcrochactus and

S. occidcntalis. The former species grows in water which varies in

depth from one to ten decimeters. In this area, and in general in the

lake region in northeastern Illinois and southeastern Wisconsin, the

Scirpus validns association grows in deeper water only when there

are no other associations of emersed plants between it and the open

water. This association is one of the commonest aquatic pioneers,

and will grow either in still water or in a moderate current. Al-

though this association agrees with the Phragmitcs-Typha association

and the Scirpus amcricanus association in having the roots in satur-

ated soil and the tops of the plants in the air, they can hardly be

grouped into a single association, as Jennings (1909:354) has

pointed out, because of the definite arrangement they always exhibit

with respect to one another. This differentiation is most evident in

the relations of the plants to the varying depths of water. The Plirag-

mites-Typha association grows in deeper water than the Scirpus vali-

dns, while Scirpns amcricanus grows in shallower water and will

persist out of the water as a relic. Where Typlia or Phraginites have

been found surrounded by Scirpus z'alidns, or vice versa, investiga-

tion has always shown a difference in level. Scirpus validus grows
in soil which contains rather more humus than that in which Typha
grows. Both associations have few secondary species, which for the

most part are unimportant. Taken as a whole, the secondary species

constitute less than 3 per cent, of the association, the remaining 97
per cent, being the dominant species. Neither Phraginites nor Typha
have more than a verj' slight ability to persist among Scirpus z'alidus

as relics, but the Scirpus itself is, to a limited extent, capable of being

an invader in the Phragmitcs-Typha, and to a greater extent pos-

sesses the power of growing as a relic in the Scirpus amcricanus as-

sociation. The color tone of the Scripns validus during the grow-
ing season is dark green, which very decidedly separates it from the

light green of the Scirpus amcricanus. The two latter associations

are shown in Figure i, Plate LIV, where Scirpus amcricanus occupies

the left half and the lower part of the right half of the figure, while

Scirpus validus, a])pearing darker in color, is in the upper part of the

right half of the figure.



328

LIST OF THE SPECIES OF THE SCIRPUS VAUDUS ASSOCIATION

Dominant Species

Scirpus validus

Secondary Species

Utricularia vulgaris auicricaiia Spart'ma inichauxiana (dwarfed
Acorns calamus (a very little on and but little of it)

the lower border) Ruiiic.v brifanuica

Relic Species

Nyuiphaea advcua (scarce) T_v/>/uj. toi/o/ia (only on the lower

border and scarce)

Invading Species

Scirpus auicricauus (on the upper border)

/

THE SCIRPUS AMERICANUS ASSOCIATION '

As has been mentioned, the Scirpus americanus association occu-

pies shallower water than the Scirpus validus association. The ac-

cumulation of humus is greater, and it is sometimes peaty in nature.

This association does not occupy ground that is pennanently out of

water, although sometimes during dry seasons it may be a decimeter

or two above the water-level. In such cases, however, the ground is

still, as a rule, thoroughly soaked by means of capillary attraction or

other agency. If this is not so, the Scirpus stems will become dry

and brown, but upon restoration of the water to its former level they

usually become green again. These light green stems give the char-

acteristic color-tone to the association. When growing in nearly pure

damp sand, the Scirpus stems are often spirally twisted—a modifi-

cation exhibited also by Juncus balticus littoralis, as mentioned on
page 277.

LIST OF THE SPECIES OF THE SCIRPUS AMERICANUS ASSOCIATION

Dominant Species

Scirpus au'.cricanus

Secondary Species

Triglochiii maritiuia Blcocharis acutn inula

Salix Candida Briophorum angustifolimn
Bidens trichospcnua tcnuiloba Rynchospora capillarca Ici'iscta

Relic Species

Alisiua plantago-aquatica Scirpus validus (scarce)



329

Invading Species

Solidago grainiiiifolia Jiuicus canadensis
Iris versicolor Hypericum virginicuui

Aspidiuin thclypteris Salix longifolia

Steironcma qitadrHlornin Asclepias incarnata
Lythniui alatuui

This association is the last of the strictly aquatic associations,

whose dominant species compose from 85 to 100 per cent, of their

area. The following are land associations in which the dominant
species are usually more numerous and more oi>enly distributed in the

area. Secondary species are much more numerous, and lead in de-

termining the different seasonal aspects of the associations. The
marsh group of associations is transitional to either prairie or for-

est.

THE CLADIUM MARISCOmES ASSOCIATION

Developing on mucky soil just back of the Scirpiis ainericaiiiis, a

little above the hight of standing water but not sufficiently high for

the surface to become dry, is the Cladium association, about 98 per

cent, of whose plants are the sedge, Cladium mariscoides. In the

youngest swales the Cladium and Scirpus amcricaiius are adjacent,

while in the middle-aged swales they are often separated by the de-

velopment of the Calamagvostis canadensis association on the ten-

sion line between them. In the oldest swales the Cladium is entirely

absent. There is seldom any mingling of these associations, even on
their border lines. The vegetation is so dense in the main part of

this association that secondary species can obtain a foothold only on
the tension line between this and other associations. In le\el places

this association will spread out to a width of 15 or 20 meters, with

a uniform structure throughout. More usually, however, it occurs

as a zone around ponds or as a belt along swales, seldom attaining a

width of one meter, but exhibiting the same uniformity of vegeta-

tional structure. During the growing season the color tone of this

association is dark green—the color of the stems and leaves. About
the first of August the plants come into bloom and the color tone is

changed to l)rown, which makes the association stand out very
sharply from the surrounding ones. This is especially the case dur-
ing years of drought, as 1908 and 19 10, when every plant of Cladium
blooms. During normal seasons, as 1909, when Figure 2, Plate LIV,
was taken, scarcely half of the plants bloom. Usually Cladium per-

sists from season to season by the growth of the root stalks. The



330

alnindant production of seeds in a dry season is a xerophytic adap-
tation.

Tlie Cladiiiin association may be displaced by a thicket, but in

nearly every case it is succeeded by the blazing star {Liatris spicata)

prairie. This latter succession takes place more easily when the Cla-
diitin is not restricted to a narrow belt. The species that invades first

are usually Lythniiii alatiiin, Solidago gratiiUiifoUa, Pxciiaiifliciiiuin

znrginiaiiitiii, OxypoUs rigidior, Gerardia paiipercula, Bpilobiiiin deii-

sum, and Liatris spicata.

LIST OF THE SPECIES OF THE CLADIUM MARISCOIDES ASSOCIATION

Dominant Species

Cladiiiui uiariscoidcs

Secondary Species

Hypericum virgiiiiaiunii (scarce) Spartina michauxiana (scarce)

Relic Species

Briophoniin aiigusfifoliitin Utricularia corniita

Scirpiis americamts Aspidium thelypteris

Invading species, nowhere abundant in this association

Lythruin alatimi

Solidago gramiiiifolia

Pycnanthcminu virginianitui

OxypoUs rigidior

Gerardia paiipcrciila

EpUobiniii densiim

Poteiifilla fruticosa

Solidago ohiocnsis

Biipatoriimi perfoliatiiiii

Stcironcma qiiadrifioruiii

Liatris spicata

Lycopus auicricanus

Lycopiis sp. ?

Osinunda rcgalis

Iris versicolor (uncommon)
Habeimria psycodes (two individ-

uals)

THE CAEAMAGROSTIS CANADENSIS ASSOCIATION

When swales have reached a sufficiently advanced stage of de-

velopment, Calamagrostis canadensis appears on the tension line

between the Cladiiiui and Scirpiis americamts associations and ulti-

mately entirely replaces the Cladium. The Calamagrostis associa-

tion occupies somewhat mucky soil in which, a little above standing

water but not sufficiently high for the surface to become dry, an

abundance of Marchantia polymorpha may occasionally be found.

It is not usually subject to inundation. From q8 to 99 per cent, of

the area of this association is occupied by the marsh grass, Calama-



331

grostis canadensis, wliose stems grow so closely as virtually to pro-

hibit the develo]>ment of secondary species. The association varies

in width from a meter or two where the slope is evident to thirty to

fifty meters or more where there is no evident slope. In all cases

the dense growth of Calamagrostis completely dominates, and the

small number of secondary species, which are usually either relics or

invaders, are notably more slender, broader-leaved, and taller than

individuals of the same species in their normal associations. This is

clearly a response to the diminution of the amount of light which

they receive, as this effect is often observed where these plants per-

sist under the shade of trees. The foreground of Figure i, Plate

LV, shows a typically developed Calamagrostis swale.

When this association obtains dominance successions are very

nearly at a standstill, since the seedlings of invaders have consider-

able difficulty in obtaining a foothold, and they must also be able to

withstand a great deal of shade. Normally the Liatris spicata prairie

is the association which should succeed. Near Zion City, however,

where the swales are occasionally burned over, the thicket association

obtains a foothold and is rapidly followed by aspens and willows.

LIST OK THE SPECIES OP THE CAEAMAGROSTIS CANADENSIS ASSOCIATION

Dominant Species

Calamagrostis canadensis

(All of the following species are very poorly represented in num-

ber of individuals)

Secondary Species

Spartina michauxiana Aster ericoides

Campanula aparinoides

Relic Species

Scirpus validus Polygonum amphibium Iiart-

Scirpus americanus
' zmghtii

O.vvpnlis ricjidior Dulichiutn arundinaccum (very

Asclcpias incarnata rare)

Invading Species

Lythnim alatum Iris versicolor

Spiraea salicifolia Mentha arvcnsis canadensis

Salix Candida Eupatorium perfoliatum

Salix longifolia



332

THE IRIS VERSICOLOR ASSOCIATION

With the draining of the stations of Carer by the lowering of the

water-level, or otherwise, the hummocks are exposed. This is usu-

ally followed by a marked increase in the number of plants of Iris

versicolor and a reduction in the amount of Carcx. Grasses, es-

pecially Foa coiiiprcssa and Poa pratciisis, spread over the hummocks,
while Iris and the secondary plants for the most part occupy the

spaces between the hummocks.
Most of the stations of this association are in the stage charac-

terized above. A few in more advanced stages indicate that if the

water-table is further lowered, the Iris association will ultimately be

replaced either by grass or by the Liatris spicata prairie association.

,In other situations, especially near the foot of the bluff south of

Beach, where the ground is more boggy, the Iris occupies a tension

zone between the carices and the thickets, persisting as a relic in case

of succession by the latter association. It is very frecjuently present

as a transition zone between the swale associations and the ridge as-

sociations, between which there are usually no successions although

they may grow in direct contact with one another.

The association is characterized by plants that prefer a somewhat
boggy soil which is always moist yet rarely inundated. The vegeta-

tion is very compact and in\'asion into it is rather slow. This associ-

ation presents conspicuous aspects during the different seasons. The
blooming of the dominant species itself characterizes the spring as-

pect. During the summer the abundant yellow flowers of Stcironcma

qiiadriflorum again make this association conspicuous. Vervain (J^cr-

bciia Jiastata), smartweed (Polycjonuiu puuctatinii), Solidago gramini-

folia, and boneset (Eiipaturiiiiii pcrfoliafimi) combine to produce the

serotional aspect, while several species, most important of which are

ladies' tresses (Spiranthes ccrmia), closed gentian (Gentiana an-

drcii'sii), Gcrardia paupercula, Gerardia tciiuifolia, and a few asters,

make up the fall aspect. Very small, single-flowered plants of Gen-

tiana proccra continue blooming late in the fall, until finally killed by

the severe frosts towards the end of Octobef.

LIST OF THE SPECIES OF THE IRIS VERSICOLOR ASSOCI.\TION

Dominant Species

Iris versicolor Elcocharis intcnucdia

Secondary species which are most abundant

Lycopiis amcricaiiiis Verbena hasfata

Stcironcma qiiadriflorum Prunella vulgaris



333

Eupaforiitni pcyfoliatuui

Epilobiiiiii dcitsiiin

SolIdago gram in ifolia

Spiroithcs ccniiia

Geutiana procera

Aspidiuin thclyptcris

Lobelia siphililica

Gcrardia paupcrcula

Secondan' species which

Lycopus sp.

HypcricH in i 'irgin icn in

Coinandra unibcllata

Gcntiana andrcivsii

Chelone glabra

Polygonum acre

Gcrardia skinncriana

Gcrardia tcnuifolia

Saturcja glabra

Cypenis rivularis

Pcnthorum sedoides

Isaiitlius brachiatus

Aster spp.

Lcersia oryzoides

Ruinex crispiis

Juncns canadensis

Cicufa bnlbifera

Cicnfa maeulata

Aster panicnlatus

Aster salicifolius

Aster spp.

Carex hystericina

Lobelia kalmii

Parnassia caroliniana

Habenaria dilatata

Habcnaria hypcrborea

are not abundant

Aster novae-angliae

Ranunculus pennsyh'anicus

Eupatoriuin purpureiim maculafum
Apocynum cannabinum liypcricifo-

litim

Cirsiiim imiticum

Habcnaria clavcllata

Habenaria Icucophaea

Osmunda rcgalis

Toficldia glutiiwsa

Polygala sanguinea

Droscra rotnndifolia

Galium boreale

Pogonia ophioglossoidcs

Symplocavpus foetid us

Cyprlpcdium hirsutuui

Pcdicularis lanceolata

Rehc Species

Calamagrostis canadensis (few)

Spartina m ichauxiana

Alisina plantago-aquatica

Invading Species

Rudbcckia liirta

Pycnantlieinuin virginianum

Lythriim alatum

Galium Irifidum

Potcntilla palustris

L\siinachia th yrsiflora

Salix Candida

Spiraea salicifolia

BetuJa puinila

THE OSMUNDA ASSOCIATION

A few patclies of Osmunda rcgalis which occur on tlie border of

the Calamagrostis association are all that remain to indicate a big as-



334

sociation wliicli lias been driven from the region. Usually the Os-

munda is between the Calamagrostis and the prairie, but it is also' be-

tween the Qncrcus velutina and the Calamagrostis, and less fre-

quently is ]3reserved as a relic in the midst of willow thickets which

have been developed in boggy ground. Osiiiiinda cinnainoinea is a

very characteristic species of this association, but it is entirely absent

from the Beach region. The only associates that have been noted

with the Osmunda rcgalis are Geraniitiu iiiaciilatuin, Fragaria inrgini-

ana, Polytrichum sp., and Zicia aiirca.

THE POTENTILLA FRUTICOSA ASSOCIATION

This northern association occurs on sandy soil which is usually

moist, although only exceptionally flooded. The association typically

follows the destruction of the pines in a soil which can supix)rt an

association genetically higher than bunch-grass prairie, but not yet

sufficiently mesophytic for the blazing star {Liatris spicata) prairie.

It often occupies the lower ground between the ridges on which the

pines are growing.

The Association.—The wide-spread growth of the dominant spe-

cies, PotentUla fniticosa, a low bushy plant, is the characteristic fea-

ture of the association. Few or no characteristic secondary species

occur, since this association is a boreal relic. Other species that may
occur are usually relics or invaders of former or succeeding associa-

tions. The composition of the invaders depends almost entirely upon
the proximity of the associations likely to succeed. In the southern

part of the region, especially towards Waukegan, this association is

so intermingled with the Liatris spicata prairie that it is difficult to

separate them. Throughout most of the year this association pre-

sents a dull, monotonous color-tone, but in the late summer it is re-

lieved by the bright yellow flowers of the PotentUla, which occur in

profusion.

Successional Relationships.—Shrubby cinquefoil {PotentUla frii-

ticosa) has more ability to invade and take possession of bunch-grass

prairie than Liatris spicata prairie, but in turn the PotentUla is al-

most immediately followed by Liatris spicata. Near the pines Po-
tentUla fruticoscL easily invades the heath and prepares it for subse-

quent prairie invasion. PotentUla fruiticosa readily takes possession of

the moister places where pines have been removed, while the heath

is characteristic of the drier places. Seedling pines {Pimts strobns)

occasionally obtain a foothold in the PotentUla fniticosa, while seed-

ling oaks (Oiiercus z'elutina) are less liable to do so. In general,

however, oaks will obtain dominance quicker in cut-o\'er pine land



335

which is not subsequently occupied by Potentilla fruticosa. In other

words, ground that is covered with a good stand of PofcntiUa fruti-

cosa is more easily invaded by prairie than by oak.

LIST OF THE SPECIES OF THE POTENTILLA FRUTICOSA ASSOCIATION

Dominant Species

Potentilla fruticosa

Secondary Species

Senccio balsamitae

Hahcnaria dilatata

Habciiaria hypcrborea

SisyritKhiuui sp.

Relic Species

Euphorbia corollata

Rudhcckia hirta

Suiilaciita stcllata

Aneiiwnc cylindrica

Lith osperinum gmelin i

Solidagp nciuoralis

Pinus strobus (by cutting)

Arab is lyrata

Potentilla anscrina

Elynius canadensis

Invading Species

Pycnanthcinuni virginianu)n

Krigia ainplcxicaulis

Liatris spicata

Pinus strobus (few)
Erigeron ranwsus
Petalostenmm candidmn
Lobelia spicata

Hypericum kahnianuni

Solidago graniinifolia

Cladonia spp.

Mosses

Artemisia caudata

Junipents horizontalis

Arctostaphylos uva-ursi

Arenaria sfricta

Ceanothus amcricanus

Calamoz'ilfa longifolia

Tradcscantia reflcxa

Pteris aqnilina

Osmunda rcgalis

Prunella z'ulgaris

Spiraea salicifolia

Fragaria virginiana

Poa compressa
Sali.v spp.

Bram us kaluiii

THE LIATRIS SPICATA PRAIRIE ASSOCIATION

Spread over the low ridges of the southern part of the Beach

area occurs the best development of the southwestern or prairie

element of the flora of this region. In the forested parts of the

region the prairie associations occupy l>elts or zones between the

swale assocations and those of the forest. The area between the

Dead Lake and the Chicago and North Western railway, whicli was



336

formerly dominated by swamp associations, is now vei"y largely being
replaced by the prairie association, which in turn is slowly giving

way to the oak forest.

Pliysical and Ecological Characteristics.—The area covered by
the prairie has an ample precipitation, distributed quite equally

throughout the year. In addition the ground is but very little ele-

vated above the surface of Lake Michigan. According to Schimper

(1903) this ought to mean that the ground is forest-co\'ered. At
the present time this is not the case, but all indications look toward
that succession ultimately. In former years, at which time the lake

le\-el was higher, this region was swampy and was occupied by
swamp associations, relics of which are easily found in the prairie

at the present time. The swamp associations formed a layer of black

soil on the sand, upon which the prairie plants spread quite rapidly

as soon as they obtained a footjiold. Lowering of the Lake Michi-

gan level has led to a partial draining of much of this land. Many
of the swamp plants can still live under the new conditions, with

prairie species, but they are gradually being displaced. As the land

is drained, more and more prairie plants have the ability to effect

ecesis even in the dense growths of swamp plants. LTnder normal
conditions oaks do not possess this ability. They can reproduce

under such conditions if the acorns are actually planted, but in the

dense coating of vegetation in swamps and prairies this rarely hap-

pens except accidentally. This explains why prairies rather than

forests came to occuiDy the swamp areas.

The Association.—This prairie association is made up of her-

baceous plants, nearly all of which die down to the ground each

year. The association is characterized by the great abundance of

individuals of a few typical species together with scattering plants

of many secondary species. The season is separated into several

well-marked aspects by the changes due to the blooming of the differ-

ent important species. The vernal aspect is characterized by phlox

(Phlox pilosa), painted cup (Castillcja coccinca), shooting star {Do-

dccatheon mcadia) and lobelia (Lobelia spicata). Phlox glaberrima

is dominant in the estival aspect. (See Fig. 2, PI. LV.) Between

the estival and the serotinal aspects occurs the blooming of Calopogon

pulchellus and Liliiuii philadclphicimi aiidiuuiii, which for a short

time produces another aspect. The serotinal aspect results from the

great abundance of blazing star ( Liatris spicata), as shown in Figure

I, Plate LVI, and by a lesser abundance of Pycnanthemitm virgini-

ciiin, Lythnim alatum, Petalostcuinm purpitrcuui, and Bryngium yiic-

cifoliimi. During the fall the blooming of goldenrods and asters.



337

but particularly Solidago ohiocnsis, characterizes the association. The
dead standing stems of many of these plants remain over winter.

Succcssioiial Relationships.—This association is preeminently an

association inhabiting low ridges which have a coating of black soil.

Accordingly it is usually able to succeed any association which forms

black soil. This is especially true in the case of the genetically high-

est swamp associations, which, in siiite of their density, the Liatris

spicata prairie is able to invade and replace as long as the water-

content factor of the soil is not prohibitive to its development. In

the more sandy swales between the ridges of pine near the lake,

shrubby plants of Potcntilla fniticosa frequently obtain dominance,

with nearly the same set of secondary species. Liatris spicata is

rather scarce at present in such areas, but shows every indication of

ultimately replacing them with prairie. As has been shown before,

a dense prairie sod prevents the invasion of oaks, but wherever it

may be broken, or near its margins, oaks can obtain a foothold. It

can readily be seen, therefore, that under the present climatic con-

ditions the final outcome of the prairie areas of this region is, or will

be, an oak forest.

LIST OF THE SPECIES OF THE LIATRIS SPICATA PRAIRIE ASSOCIATION

Dominant Species

Liatris spicata

Phlox pilosa

Phlox glabcrriiiia

Castillcja coccinca

Dodccathcon mcadia

Lilinm philadclphiciiiii andiuiiiii

Pycnanthcmum virginiantiiii

Lythruiii alatinii

Secondary Species

Aletris fariiiosa

Apocyiv.iiu cauiiabiiiiiiii Iiypcrici-

foliitm

Aster novac-angliac

Aster ptarmicoides

Aster spp.

Calopogoii pulchcUus

Brigcron rainosiis

Erigeron philadelphiciiin

Bryngiiim yiiccifoHinii

Solidago ohioeiisis

Solidago riddcUii

Ritdbcckia hirta

Senccio balsamitae

Sorghastnnn nutans

Andropogon furcatus

AUiiiin cernmnii

Pctalostcmutn piirpiireiiiu

Anemone xnrginiana

Aster diDuosus

Astragalus canadensis

Bronius kalmii

Coniandra untbellata

Dcsinodinin- iilinoense

Coreopsis lanceolata villosa

Coreopsis paUnata

Bupatoriuni pcrfolialuui

(abundant)



338

Euphorbia coroUata (abundant)

Fragaria z'irginiaiia

Helenium antumnale
Hcitchera hispida

Hicrochloc odorata

Hypoxis hirsiita

Lactuca canadensis

Lcspede:;a capitata

Liatris cylindracea

Lobelia siphilitica

Lobelia spicata

Poa compressa
Poa pratcnsis

Potcntilla argnia

Runie.v crispits

Sisyrinchium sp.

Solidago grauiinifolia

Solidago scrotina

Solidago speciosa

Solidago speciosa angustata

Vicia americana

Valeriana ediilis

Zizia a urea

Relic species in normal genetic

Acerates virididora

Aniorpha caiicscens

Arabis lyrata

Arctostaphylos iiva-tirsi

Junipenis coniniunis depressa

J 11 II
i
perns horizontalis

Aspidiuin thclypteris

Aster azurciis

Calaiiioz'ilfa loiigifolia (rarely)

Elyinns canadensis

Euphorbia corollata

Gerardia feniiifolia

Gerardia panpcrcnla

Gerardia skinnc riana

Hypericum kalmiannm
Koeleria cristafa

Bctiila alba papyrifcra

Eupatoriiiin piirpureum

. niacidatuiii

Glyceria nervata

Helianthus grosseserratus

Hclianthus occideiitalis

Helianthus iiia.riiiiiliaiii

Krigia aiiiple.vicaulis

Lathyrus palnstris viyrtifolius

Lepachys piniiata

Liliuin canadcnse

Pedicnlaris lanceolata

Petalosteniiiin candidniii

Polygala polygama
Polygala irrticillata

Prenanfhes raeemosa
Satureja glabra

Silphiuui intcgrifoliuin

Silphium terehinthinaceiiiii

Tofieldia glutinosa

Tradescaiitia reflexa

Vernonia fasciculata

Viola papilionacea

Viola sagittata

Scleria verticillata

succession

Achillea iiiiUefoliiiiu

Andropogon scoparius

Arenaria stricta

Artemisia caudata

Aselcpias iiicarnata

Asclepias purpurasccns

Asclepias syriaca

Asclepias tuberosa

Carex oederi puiiiila'

Carex spp.

Eupatoriitm pcrfoliatuin

Habenaria claveUata

Habenaria dilatata

Habenaria leucophaea (3 plants)

L-is x'crsicolor

Licifris scariosa*

Caiiipainda apariiioides

i



339

Bctula putnila

Jiincits balticits littoralis

Jicncus canadensis

Juncus torreyi*

Osmunda regalis

O.vypolis rigidior

Parnassia caroliniana

Polygoniiin hydropipcroides

Potcntilla anscrina

PotentiUa fritticosa

Rynchospora capillacea Icvisefa

Scirpus ainencanits

Scirpiis atroi'ircns

Scirpus lincatus

Solidago neinoralis (scarce)

Steironcma quadriflorum

Relic species remaining after

Anemone cylindrica

Heracleiini lanatnni

Pediciilaris canadensis

Prunella vulgaris

Siirilaciiia stcllata

Linuui z'irginianiini

Lithosperniuin gniclini (scarce)

Lobelia cardinalis

Lycopus amcricanus
Panicuvi zirgatum
Pinus strobus

Pimis laricio

Pinus sik'estris

Rhus toxicodendron

Sali.v Candida

Salix glaucophylla

Salix syrticola

Scleria triglomerata

Spartina luichauxiana

Alisuia plantago-aquatica

the removal of oak groves

Ccanothus amcricanus

Monarda uiollis

Podophyllum pcltatum

Pteris aquilina

Smilax ccirrhata

Invading species of the thicket associations

Cirsium inuticum Cornus stolonifcra

Populus deltoidcs Rhus hirta

Popuhis tremuloides Salix cordafa

Sambucus canadensis Salix discolor

Spiraea salicifolia Salix pedicellaris

Salix spp.

Invading species of the woods

Quercus velutina Sanicula marilandica

Carya oz'ata (a few seedlings) Geum canadcnsc

Vitis znilpitm Agriuioiiia gryposcpala

Species of accidental occurrence

Ambrosia artcmisiaefolia Bromus fectorum

Convolvulus scpium Salsola hall tenuifolia

Trifolium repens

*The two species marked with an asterisk also play the r6!e of invaders where
the water-table is being lowered beyond the requirements of the Liatris spicata
prairie.



340

THE JUNCUS TORREYI ASSOCIATION

This small association, composed virtually of only the dominant

species, occupies very definitely the tension line between the blazing

star (Liatris spicaia) and the Liatris scariosa associations. It may
extend slightly into both of them, but in such cases is evidently act-

ing as an invader in one and a relic in the other. This depends upon

which Liatris association is succeeding the other, since that succes-

sion is reversible and bears a seemingly definite relation to elevation

or depression of the water-table. The large dark green to brown
heads of the dominant species make this association stand out very

distinctl}^ from each of its neighbors. The usual width of the asso-

ciation is five to twenty-five centimeters, though it may be greater

or less according to the slope of the land. In blowouts where neither

Liatris is present, this Jnnciis occupies very definitely the median
position between the sets of plants which represent those two associa-

tions.

LIST OF THE SPECIES OF THE JUNCUS TORREYI ASSOCIATION

Dominant Species

Jnnciis torreyi

Relic or Invading Species (depending on the direction of succession)

Rynchospora capillacca Icviscfa Stcironciiia quadriflonim

The Thicket Associations

the p0pulus-s.a.lix-c0rnus thicket association

This association is one of the usual steps in the succession from

marsh to oak forest. It is cpite general in its distribution througli-

out the central part of the Beach area. It may invade almost any as-

sociation, but it is most successful in the Liatris spicata, Calamagros-

tis canadensis, Iris versicolor, and blowout associations.

Physical and Ecological Characteristics.—This association grows

in soil varying from sandy loam to the black soil of the prairie. The

water supply is always ample on account of the proximity of the

water-table level of Lake Michigan. The growth of the thickets is

very dense, and in the protection thus afl^orded considerable huiuus

may be formed.

The Association.—The association is composed of any one of

the dominant species or of different combinations of them. Dogwood
(Corniis stolonifera) and the species of willow (Sali.v) are each

much more abundant than the species of Populiis. There seems to



341

be no particular arrangement of tlie dominant species wlien they oc-

cur together, except in tlie more pronounced ridges. Here Popiilus

occupies the crest and Salix and Coniiis the slopes. With them are

a number of secondary species, many of which are either invaders

of the forest type of vegetation or relics of the prairie.

Siicccssional Rclaliotiships.—On sandy ground this association is

very frequently introduced by the invasion of cottonwood ( Populus
dclfoidcs), followed by species of Salix and Coniiis. In black soil,

species of Salix or Coiiius are more usually the pioneer invaders.

Succession is accomplished b}' the cutting-off of the light supply from
the vegetation below as soon as the shrubs attain sufficient size. In

due course of time some of the species of Salix and Populus become
trees, with almost the same assemblage of secondary species, but ul-

timately the thickets occurring on the beach plain will be replaced

by the Qucrcus z'clutiiia association, while those near the base of the

bluffs will be replaced 1iy the oak-hickory woods.

LIST op THE SPECIES OF THE POPULUS-S.\LIX-CORNUS

THICKET ASSOCIATION

Dominant Species

Coruus stolonifcra

Populus tremuloidcs

Populus dclfoidcs

Rosa Carolina

Salix auiygdaloides

Salix cordafa

Secondary Species

Aster uuibellatus

Aster novae-aiigliac

Bctula alba papyrifcra

Bctula puuiila

Broiuus incaiius (i plant)

Dioscorea paiiiculata

Eqiiisctuin ari'ense

Helianthus occidentalis

f. illinocims

Helianthus grossescrralus

Lactuca canadensis

Lcchea leggcttii

Relic Species

Achillea luillcfoliuiu

Salix discolor

Salix longifolia

Salix lucida

Salix pedicillaris

Salix scrissinia

Lechea villosa

Lonicera dioica

Prunus scrotina

Ribes sp. ?

Rhus toxicodendron

Rhainnus alnifolia

Rub us ocddcntalis

Spiraea salicifolia

Solidago canadensis

Solidago scrotina

Sa)nbucus canadensis

Silphiuni intcgrifoliuui

Lespedeza capitata



342

Agrnstis alba

Amorpha caucsccns

Andropogon fiircatus

Asclcpias incarnata

Asclepias syriaca

Asclepias tuberosa

Aspidimn thelypteris

Aster asureus

Aster dinnosus

Betnla alba papyrifera

Betiila pumila

Calopogon pulchcllus

Desmodiuiii ilUnoense

Brigeron raiiwsus

Eiipatoriimi purpiireuiii luacit-

latiim

Euphorbia corollafa

Habeiiaria psycodes

Junciis balticiis littoralis

Koeleria cristaia

Krigia amplexicaulis

Lathyrus [^ahistris viyrfifolius

Invading Species

Acer negundo
Acer saccharinum

Aralia luidicaulis

Bchinocystis lobata

Geranumi inaciilatiiiii

Maiantheuium caitadeiise

Garya 07.'aia

Liatris spicata

Lobelia spicata

Lythrum alatuin

Oxypolis rigidior

Paiiicum I'irgaium

Parnassia caroliniana

Pcdicularis lanceolata

Petalosteiuum caJididiDii

Potentilla fniticosa

Prcnanthes raccinosa

Primus pumila

Pycnanthemuui virginianum

Ry>iclwspora capillacea Icz'iscta

Rndbeckia liirta

Salix glaucophylla

Salix syrticola

Sileiie antirrhina

Solidago ohiocusis

Solidago grauiinifolia

Sorghastriiiii nutans

Tradescantia reflexa

Zisia a urea

Monarda fistulosa

Polygonatum coiniuufatuui

Oucirus %'elutina

Sinilacina stellata

Siu ilax h ispida

Vitis vulpina

Juglans nigra

THE PRUNUS THICKET ASSOCIATION

While over go per cent, of the tliickets of this region belong to the

Populus-Salix-Cornus thicket association, there are, along the north

bank of the Dead Lake, a few thickets which belong to a different

association. Their position and composition are about the same as

the sand river-bank thickets occurring along the Mississippi River

in the vicinity of Hanover, Illinois, described by Gleason (1910:142).

The bushes form the dominant part, but mixed in with them are

lianas, which in places make the vegetation difficult to penetrate. The
ground is sandy at the surface, although below it may be somewhat



343

loamy. These thickets grow in and around tiie borders of the pines,

effectually cutting off their chances of reproduction. The central

parts of the thickets are too dense for the ecesis of oaks, but towards
the edge, where it is more open, black oak, Querciis velutina, cjuite

readily obtains a foothold and in time replaces the thicket.

The marked differences between these two kinds of thickets are

the possession of lianas and the sandy-appearing soil in the Primus
thickets, while the Popiilits-Salix-Corniis thicket, with virtually no
exceptions, is free from lianas and has somewhat loamy or mucky
soil.

LIST OF THE SPECIES OF THE PRUNUS THICKET ASSOCIATION

Dominant Species

Primus puinila Prunus virginiana

Prunus serotiiia Sauibucus canadensis

Secondary Species

Lianas

:

Vitis vulpina Rhus toxicodendron radicans

Celastrus scandens

Herbaceous plants

:

Anemone canadensis

Asparagus officinalis

Aster spp.

Fragaria virginiana

Relic Species

Calainoi'ilfa longifolia

Euphorbia coroJlata

Oenothera rlionibipetala

Phlox pilosa

Poa compressa

Pofentilla fruticosa

SoUdago nemoralis

Invading Species

Qucrcus velutina

Lathyrus venosus

Veronica virginica

Melilotus alba

Rosa huniilis

Artemisia caudata (few)

Juncus balticiis littoralis

Koeleria cristata

Pctalostcunmi purpurcuni

Salix glaucophylla

Polygonatuni biftoruui (where

oaks have been cut)

Up to the jiresent point, the discussion of associations has been

limited to those of the sand-i)lain. The bluffs which constitute its

western boundary are tenanted Ijv arboreal associations which show

an inclination to invade the prairie, although, up to the present



344

time, very little has been accomplished. The most widely distributed

is the oak-hickory association, in which the following species are

the most important: bur oak (Oucrciis iiiacrocarpa), red oak {Qitcr-

ciis rubra), white oak (Qiicrciis alba), shell-bark hickory {Carya

ovata), Carya cordifonnis, and Jiiglans nigra, together with many
secondary species. It is an association of essentially loam}- or clayey

soil, ancl does not readily invade the sandy areas. On moister

ground occurs a more mesophytic association of trees, the Uliniis-

Acer association, whose characteristic species are elm ( Uliniis aineri-

t"a);a), soft maple (Acer saccharimiiii), basswood (Tiiia aiiicricana),

and white ash {Fraxiiius aiiicricana). This in turn is succeeded by

the climax association of this region, the sugar maple (Acer sac-

charmii) association, which at the present time is in the infancy of

its development in northeastern Illinois.

The following cross-sections, or transects, taken in the southern

part of the region, will aid in the understanding of the region. The
sections were obtained by listing the changes in the associations, while

walking across the area from east to west.

SECTION OF THE ASSOCIATIONS OP THE BEACH AREA MADE ALONG THE

LINE OF THE VVAUKEGAN SEWER, AUGUST, I909

1. Lake Michigan.

2. Open sand of lower beach.

3. Beach pool with Clilainydoiiionas and Oscillatoria.

4. Open sand.

5. Cakile-Xanthiitm association on the middle beach.

6. Salix syrticola dune.

7. Pofciitilla anscrina association.

8. Salix syrticola dune with a little Calamovilfa.

9. Andropogon scoparius bunch-grass prairie.

10. Popnlns-Salix dune, o.i to 0.4 meter high.

11. Calainoznlfa growing on the edge of bunch-grass prairie.

12. Andropogon scoparius bunch-grass prairie.

13. Calamovilfa ridge.

14. Bunch-grass prairie with a few very low Calamovilfa ridges.

15. Potcntilla friiticosa association.

16. A thicket of Salix.

17. A swale.

18. Popidiis-Salix ridge.

19. Heath.

20. Heath with blowouts and a little Calamovilfa.

21. Scirpus amcricaiius association.



23

24

25
26

27
28

29
30
31

32

33

34

35
36

37
38

39
40
41

42

43
44
45
46

47
48

49

345

Scirpiis z'alidiis association.

Typha latifolia.

Castalia-Ny IIIpliaca association.

Potamogeton nataiis association.

Little Dead River.

Nyiiiphaca advcna.

Typha latifolia.

ScirpKs validus association.

Scirpiis ainericanus association.

Liatris spicata prairie.

Scirpiis ainericanus association.

Panicum virgatum ridge.

/uncus torrcyi association.

Liatris spicata prairie.

Jiinciis torrcyi association.

Scirpiis Z'alidiis association.

Typha latifolia.

Scirpiis ainericanus association.

Elgin, Joliet and Eastern railway.

Swale, whose structure was exceedingly complex.

A ridge which had Ijeen cleared and was covered with weeds,
including especially Polygomiin oricntale and Hcliaiithtts

annuus.

Liatris spicata prairie.

Phraginites-Typha swamp, eighty feet wide.

Scirpiis Z'alidiis association.

Scirpiis ainericanus association.

Chicago and North Western railway.

Cultivated land.

Ulniiis-Accr association at the foot of the bluff.

Bluff co\ered for the most part with oak-hickory woods.

SECTION MADE ALONG THE LINE OF THE PEST-HOUSE R0.\D

BETWEEN WAUKEGAN AND BE \CH, AUGUST, I909

Lake Michigan.

Lower beach, devoid of plants.

3. Middle beach, bare except for an occasional Xanthiuiii.

4. Sali.x- syrticola fringing dune.

5. Depression.

6. Small Popiilus-Salix dunes.

Andropogon scopariiis bunch-grass prairie.

Calainnz'ilfa dune.



346

9- Bunch-grass prairie.

10. Heath represented by Arctostaphylos.

11. Bunch-grass prairie.

12. Heath of Arctostaphylos.

13. Calauwz'ilfa dune.

14. Bunch-grass prairie.

15. Heath of Arctostaphylos and Jmiipcrns.

16. Potentilla fruticosa association.

17. Jiincus torreyi association.

18. Cladiiiui viariscoidcs swale.

19. CaJantoznlfa dune, mostly supplanted by heath.

20. A suggestion of Liatris spicata prairie by ToUeldia.

21. Heath.

22. Jitncits torreyi.

23. Cladiitm swale.

24. Liatris spicata prairie.

25. Jiincns torreyi association.

26. Cladiiiui swale.

27. Liatris spicata prairie.

28. Scirpus aniericanns association.

29. Potamogcton association.

30. Jitnciis torreyi association.

31. Liatris spicata prairie.

32. .tunciis torreyi association.'

33. Scirpus atiicricanus association.

34. Cladiuui mariscoides association.

35. Scirpus auiericanns association.

36. Scirpus z'alidus association.

37. Nymphaca adveua.

38. Open water.

39. Scirpus z'alidus association.

40. Scirpus auiericanus association.

41. Liatris spicata prairie.

42. Cladiuui swale.

43. Liatris scariosa association with blowouts.

44. Scirpus aiuericaiius association.

45. Cladiuui swale.

46. Liatris spicata prairie.

47. Cladiuui swale.

48. Liatris scariosa ridge with a few relic pines.

49. Calaiuagrostis canadensis association.



347

50-

51

52

53

54

55
56

57
58

59
6o
6i

62

63

64

65
66

67
68

69
70

73

74

75
76

77
78

79
80,

81

A ridge with Calamovilfa, Betula alba papyrifera, and
Juniperus.

Cladiimi swale of considerable width.

Scirpiis aniei'icanus association.

Sdrpits ralidiis association.

Sogitfa ria la t ifolia.

Liatris spicata prairie.

Scirpiis z'alidus association.

Typha latifolia association.

Sagittaria latifolia.

Liatris spicata prairie giving way to thicket.

Scirpiis z'alidiis association.

Typha latifolia.

Scirpiis validiis association.

Liatris spicata prairie with a few relic pines.

Scirpiis validus swale.

Liatris spicata prairie on a ridge.

Scirpiis z'alidus association.

Liatris spicata prairie.

Scirpiis Z'alidus association.

Cliicago and Xortli Western railway.

Typha latifolia.

Calaniagrostis canadensis association.

Sali.v thicket.

Calaniagrostis association.

Salix thicket which has followed Liatris spicata.

Scirpiis Z'alidus association.

Phraguiifc.<;-Typha association.

Scirpiis Z'alidus association.

Sali.r thicket.

Scirpiis Huviatilis.

Populus-Sali.v thicket.

Bluff woods, of oaks and In'ckories for the most part.

A section taken north of Beach would show, behind the dune-

conijilex, ridges of Qucrcus z'clutina alternating with thickets and

witli ])rairie for a distance of about 0.8 km. from the lake. Between

the last ridge of oaks and the railway, areas of prairie alternate with

areas of swamp. Sections taken farther north become simj^ler, and

contain fewer and fewer associations until, near Kenosha, the bluft

is cut into bv the lake.



348

General Conclusions

Consideration of the foregoing data makes evident the sncces-

sional relations of the three floral provinces represented in the Beach
area. And what holds good for this area is applicable to north-

eastern Illinois and southeastern Wisconsin in general, as miglit nat-

urally be expected. Over the greater part of this general region

there is a greater extent of prairie than of forest, but in the Beach
afea, forests occupy about half the gromid. The larger part of the

forest is the deciduous forest of the southeastern center of dispersal.

Successions clearly show that there have been times in the past

when each one of these provinces was more widely extended than
is now the case. This is particularly true of the prairie and the coni-

fer forest, for they are gradually being reduced in extent througli

natural causes which at the same time favor the increase of the de-

ciduous forest. Aside from wave action the factors that tend toward
the destruction of the deciduous forest are all connected with the in-

roads of man.

Before going furtlier into detail, a recapitulation of the pertinent

characteristics of the vegetation of the different floral provinces is in

order.

Prairie Province.—The vegetation is less than two meters, usually

about one meter, in hight, consisting of grasses and herbs usually as-

sembled very closely together, often forming sod. The plants will

stand a considerable variation in the moisture content of the soil but

require virtually the maximum amount of light.

Deciduous Forest Province.—The dominant plants are deciduous

trees, in the more xerophytic associations, such as are represented in

this region, rather openly assembled, giving all variation in shade,

usually with little or no sod. The ground vegetation is open, and

often consists of a number of plants whose showy flowers constitute

the seasonal aspects. The seedlings are rather intolerant of shade,

but otherwise develop very readily. Once established on this sandy

soil, associations of this province are usually pennanent.

Northeastern Conifer Forest Province.—The plants are ever-

green trees or prostrate evergreen shrubs, growing in sandy soil in

more or less closed assemblages. The denser assemblages of trees

cast so much shade that all undergrowth is prohibited and the ground

is carpeted with pine needles. Where the assemblages are more open,

there are numerous herbaceous plants. With the exception of a very

few local stations, the pines of this region are not reproducing them-

selves. On the other hand, the heath plants reproduce readily, by



349

seeds as well as through vegetative means, on the more xerophytic

soils.

With these characteristics in mind, consideration can now be
given to the different lines of succession that are theoretically pos-

sible between the associations of the three provinces. The possible

successions are indicated below, and will be taken up in corresponding
order.

Prairie

Conifer forest

Deciduous forest

conifer forest

deciduous forest

prairie

deciduous forest

prairie

conifer forest

As this region is nominally placed in the prairie on maps of vegeta-

tion (by Pound and Clements, Engler, Transeau, Sargent, and others),

the successional relationships of the prairie will be taken up first. In

this region the prairie should not be replaced by the conifer forest, as

it is south of the natural range of that province. Locally, where
the prairie sod has been accidentally broken, young pines are occa-

sionally found, but as the occurrence is so plainly accidental, and tak-

ing into consideration other facts of the region, it is perfectly justi-

fiable to say that in this region the prairie will never be succeeded

by conifer forest.

In the case of the deciduous forest, matters are different. Prairie

and deciduous forest are everywhere in juxtaposition, which results

in the shading of the edges of the prairie. This occasions the grad-

ual breaking up of the normally dense prairie growth, permitting the

occurrence of open places in which the deciduous forest can readily

take hold. Such succession is very slow. Occasionally an oak will

efifect ecesis in the body of the prairie itself—the result of accidental

planting, probably by crows or jays. Once started, nothing but acci-

dent prevents the development of mature trees, which by their in-

creasing shade modify the prairie radially and serve as a nucleus for

the spread of the forest. As long as the prairie sod remains intact,

however, this succession can not take place. Yet, notwithstanding

the fact that things are changing slowly, it is apparent that, under



350

present climatic conditions, tlie prairie of tiiis region will nltimately

give place to the deciduous forest.

In dealing with the conifer forest province it must be kept m
mind that the area is several (130) kilometers south of the southern

limii^. of the province in eastern Wisconsin, and virtually no invasion

^y if into other provinces could be expected. The cpiestion is whether

or not it can hold its own. In the case of the prairie this question

is usually decided in the affirmative, as the prairie can not exist m
the dense shade of the conifers. It spreads into the pines only when
some of their number die. Then it takes possession of the open spaces

and prevents rei^roduction of the pines, so that with the dying of the

old trees the prairie is left supreme. (Fig. 2, PI. LVI.)
Seedlings of the oak Quercus vclntina, are present almost

throughout the area of the pines, w'ith the exception of the very

densest parts. While usually only the oaks in the open places de-

velop, the continual presence of seedling oaks under the pines means
that whenever a pine dies, in a short time its place is occupied by a

number of oak trees, under whose shade the seedling pines—few in

number at best—can not develop. It is therefore clearly evident that

in this region the remaining representatives of the conifer forest

province will ultimately be replaced by trees, representative of the

deciduous forest province.

These same general statements, slightly modified, hold true for the

heath association, a member of the conifer forest province.

The typical heath plants are somewhat more lenient in their

ecological demands than the coniferous trees, which signifies,

however, only that a much greater length of time will be nec-

essary to efifect their elimination from the region. As long

as the prairie growth is fairly open, the heath and prairie

plants thrive together, but a dense prairie growth is very efficient in

choking out the heath. Heath plants are only fairly tolerant of shade;

but as long as the open black oak woods prevail, the heath can read-

ily persist in the open places. Greater shading eliminates bearberry
{Arctostaphylos), but Junipcnis horizontalis and especially /. co;»-

munis dcprcssa can exist even in the much denser shading of a bur
oak {Quercus macrocarpa) woods. Here, however, they are etio-

lated in response to the diminution of light, and show the other char-

acteristic modifications induced by shade, namely, broader, flatter

leaves which spread more, making a looser and weaker growth.
The deciduous forest—now occupying nearly half of the Beach

area—is the natural climatic floral province to be expected in this

region with the present conditions of climate. In all natural sue-



351

cessions this province maintains its dominance. The prairie can not

naturally supersede it because the climatic conditions are suitable for

the development of forests, and the prairie, as a unit, can not make
headway under shade. Conifers can not succeed the deciduous for-

est because they can not reproduce themselves in it.

In view of these facts, it is plainly evident that, under the pres-

ent conditions of climate, the deciduous forest province is the domi-
nant one in this region, and if left to itself in nature would ulti-

mately occupy the entire region.

Summary

1. The Beach area is a strip of low sandy land bordering

Lake Michigan in northeastern Illinois and southeastern Wisconsin.

Its length is about 14 miles and its extreme width is a little over a

mile. Its maximum elevation above Lake Michigan is less than 30
feet.

2. This region lies a little way south of the southern limits of

the Northeastern Conifer Province, within an area of competition

between the Prairie and Deciduous Forest provinces, in a climate

which is favorable to tree growth.

3. During postglacial times the entire region was submerged,
and within the past eighty years the region has at times been virtu-

ally inundated.

4. The region contains 55 ])lant associations, representing three

plant provinces: Northeastern Conifer, Prairie, and Deciduous For-
est.

5. A study of the successions between the different plant asso-

ciations gives a very satisfactory understanding of plant dynamics.
6. The two fundamental starting-points for genetic series are

the open water of Lake Michigan and of the streams that flow into

it. The lines of succession commence with open water and proceed
through stages of progressively increasing dryness, which culminates,

in the Beach area proper, in the black oak association. The interme-
diate steps group themselves along several genetic lines.

7. Commencing with Lake Michigan, one genetic line extends from
acjuatic algae through associations inhabiting progressively drier soil

in the depressions and swales between the ridges. Another line be-
gins with the plants that inhabit the open beach, where they are ex-
posed to extreme xerophtic conditions, because of a continual addition
to the food in the soil, and advances to associations of an incrcasin"-

number of species and a higher type of vegetative development. A
third line commences in the streams with plants which are wholly



352

submerged, and proceeds through associations of plants which are

progressively less hydrophytic to those which are mesophytic.

8. A change in the water-table level—whether brought about

by special factors, as local erosion, blowing away or piling up of

sand, or general factors, as periodical fluctuations in the level of Lake
Michigan'—very materially aids the plant dynamics in bringing about

these successions.

9. The establishment of a genetic series may be initiated by
nearly any of its lower members, while the advanced stages are de-

pendent upon preceding associations for a foothold.

10. Favorable chances for invasion are usually readily taken

advantage of, while the unfavorable periods of the lesser climatic

cycles tend to produce adaptations to those conditions rather than a

reversal of the normal line of succession.

11. Aquatic associations have a relatively greater number of

individuals of a much smaller number of species than land associ-

ations.

12. Associations in the middle of a true genetic series are com-
posed of a larger number of species than the associations towards the

beginning or towards the end of the series.

13. Although most of the aquatic and semiaquatic plants are

closely restricted within certain depths of water, their position in any
given locality is determined by competition of associations rather

than by the different physical requirements of the plants. The same
relative arrangement is maintained within the limits of the require-

ments of the individual plants in different localities, even though the

absolute conditions may vary greatly.

14. When associations within one formation are concerned, suc-

cession usually begins by the invasion of the secondary species of the

invading association, and the succession may be said to be completed

when the dominant species have made their appearance.

15. In the case of the invasion of an association of one forma-

tion into an area occupied by an association of another formation,

invasion is effected by the dominant species with the subsequent ap-

pearance of the secondary species. Invasion of one fomiation into

another takes place through the genetically lower, or pioneer asso-

ciations.

16. In the Beach area, either the black oak or the prairie may
displace the conifers; the prairie also gives way to the deciduous

forest. Associations of the marsh habitats usually go through a prai-

rie stage before becoming forested by deciduous trees.



353

List of the Species of Plants Growing on the Beach Arf^

This list is arranged in systematic order, with the collection num-
bers of those collected. The nomenclature is that of Gray's Manual,

/th edition. Synonyms are given in parentheses.

THALEOPHYTA

Chlamydomonas sp. ?

Oscillatoria sp. ?

Chara sp. ? (3202)
(No other genera of algae were determined)

BRYOPHYTA

Riccia fluitans L,. (3217)
Marchantia polymorpha L. (3151) Liverwort

Polytrichum juniperinum Willd. (2744) Moss

(No other species were determined)

PTERIDOPHYTA

Polypodiaceae. Fern Family.

Pteris aquilina L. Bracken Fern

Aspidium thelypteris (L.) Sw. (2501, 2801, 2929) Marsh Fern

Osmundaceae. Flowering Fern Family.

Osmunda regalis L. (O. spectabilis Willd.) (1652, 2765) Royal Fern

Equisetaceae. Horsetail Family.

Equisetum arvense L- Horsetail

Equisetum laevigatum A. Br. Scouring rush

Equisetum hiemale L. (3041) Scouring rush

SPERMATOPHYTA

Pinaceae. Pine Family.

Pinus strobus L. (2483, 2809, 2905) White Pine

Pinus laricio Poir. (2841, 2903) Austrian Pine

Pinus silvestris L- (3165, 3205) Scotch Pine

Pinus sp.

Larix decidua Mill. (2460, 2842) Tamarack



354

Juniperus communis depressa Pnrsh. (1659, 2843, 2907) Juniper

Juniperus horizontalis Moencii. (1658) Procuml^ent Juniper

Juniperus virginiana L. (2910) Red Cedar

Typhaceae. Cattail Family.

Typha latifolia L. (3091) Cattail

Typha angustifolia L. (2824) Narrow-leaved Cattail

Typha latifolia x angustifolia (2915)

Sparganiaceae. Bur-reed Family.

Sparganium eurycarpum Engelm. (2831) Bur-reed

Naiadaceae. Pondweed Family.

Potamogeton natans L. Pondweed
Potamogeton foliosus niagarensis (Tuckerm.) Morong. (3246) Pond-

weed

Juncaginaceae. Arrow Grass Family.

Triglochin maritima L. (2515) Arrow Grass

Triglochin palustris L. (2867)

Alismaceae. Water-plantain Family.

Sagittaria latifolia Willd. (2908) Arrowleaf

Sagittaria heterophylla rigida (Pursh) Engelm. Arrowleaf
Alisma plantago-aquatica L. (2902) Water-plantain

Hydrocharitaceae. Frog's Bit Family.

Elodea canadensis Michaux. Water-weed

(Gramineae) Poaceae. Grass Family.

Andropogon scoparius Michx. (2921) Beard Grass

Andropogon furcatus Muhl. (2940) Beard Grass

Sorghastrum nutans (L.) Nash. (2966)
Digitaria sanguinalis (L.) Scop. (3257) Finger Grass, Crab Grass

Panicum capillare L. (3232) Witch Grass, Old-witch Grass

Panicum virgatum L. (2938) Switch Grass

Panicum huachucae Ashe. (3224)
Panicum scribnerianum Nash. (3065)
Echinochloa crusgalli (L.) Beauv. (3209) Barnyard Grass

Cenchrus carolinianus Walt. (2980) Sandbur
Leersia oryzoides (L.) Sw. (2985) Rice Cut-grass



855

Hierochloe odorata (L.) Wahlenb. Vanilla Grass

Stipa spartea Trin. (2464) Porcupine Grass

Aristida purpurascens Poir. (3260)
Phleum pratense L. (3064) Timothy
Sporobolus cryptandrus (Torr.) A. Gray. (3255) Drop-seed

Sporobolus heterolepis A. Gray. (3223)
Agrostis alba L. Red Top.

Calamovilfa longifolia (Hook.) Hack. (2920)
Calamagrostis canadensis (Michx.) Beauv. (2823) Reed Grass,

Blue-joint Grass

Ammopbila arenaria (L.) Link. (3201, 3281) Beach Grass

Koeleria cristata (L.) Pers. (2467, 2763)
Spartina michauxiana Hitchc. (2913) Slough Grass

Phragmites communis Trin. (3166) Reed
Poa compressa L. (2860) English Blue Grass

Poa pratensis L. (3037) Blue Grass, June Grass, Spear Grass, Ken-
tucky Blue Grass

Glyceria nervata (Willd.) Trin. (2810)
Festuca octoflora Walt. (2468) Fescue Grass

Bromus tectorum L.

Bromus incanus (Shear) Hitchc. (3173)
Bromus kalmii Gray. (2762, 2795) Wild Chess

Elymus canadensis L. (2879, 2880) Wild Rye

Cyperaceae. Sedge Family.

Cypenis rivularis Kunth. (2986) Sedge

Cyperus schweinitzii Torr. (3149)
Cyperus filiculmis macilentus Fernald. (3147)
Dulichium arundinaceum (L.) Britton. (3261)
Eleocharis acuminata (Muhl.) Nees. Spike Rush
Eleocharis intermedia (Muhl.) Schultes. (2926)
Fimbristylis castanea (Michx.) Vahl. (2814, 2863)

Scirpus americanus Pers. (2508, 2856.) 3-angle Bulrush

Scirpus validus Vahl. (2862, 2865) Great Bulrush

Scirpus occidentalis (Wats.) Chase. (Collected by Dr. H. A. Gleason

and determined by Mrs. Chase.)

Scirpus fiuviatilis (Torr.) Gray. (2785) River Bulrush

Sciqius rubrotinctus Fernald. (3059)
Scirpus atrovirens Muhl. (2770)
Scirpus lineatus Michx. (2836)
Eriophorum angusti folium Roth. (E. polystachion L. in part) (1669,

2523) Cotton Grass



356

Rynchospora alba (L.) Vahl. (Collected by L. M. Umbach, July

31, 1909-)
Rynchospora capillacea leviseta E. J. Hill. (2851, 2925) Beak Rush
Cladium mariscoides (Muhl.) Torr. (2857, 2868, 2916) Twig Rush
Sderia triglomerata Michx. (2772) Nut Rush
Scleria verticillata Muhl. (3210)
Carex bebbii Olney. Sedge
Carex aurea Nutt. (2503)
Carex buxbaumii Wahl. (2504)
Carex comosa Boott. (2917)
Carex cravvei Dewey. (2502, 2821)
Carex filiformis L.

Carex hystericina Muhl. (2787)
Carex lanuginosa Michx. (3027)
Carex muhlenbergii Schk. (2465, 3163)
Carex oederi pumila (Cosson & Germain) Fernald. (C. viridula

Michx.) (2509, 2517)
Carex riparia W. Curtis. (2786)
Carex stipata Muhl. (3052)
Carex stricta Lam. (2498)
Carex trispenna Dewey. (Collected by Dr. H. A. Gleason)
Carex umbellata Schk. (2474)

Araceae. Arum Family.

Symlocarpus foetidus (L.) Nutt. (3062) Skunk Cabbage
Acorus calamus L. (2766, 2897) Sweet Flag

Lemnaceae. Duckweed Family.

Lemna minor L. (3218) Duckweed

Commelinaceae. Spiderwort Family.

Tradescantia reflexa Raf. (3022) Spiderwort

Pontederiaceae. Pickerel-weed Family.

Pontederia cordata L. Pickerel-weed

Juncaceae. Rush Family.

Juncus bufonius L. (2782) Rush
Juncus tenuis Willd.

Juncus balticus littoralis Engelm. (2882, 2923, 3250)
Juncus canadensis J. Gay. (2848, 2850)
Juncus torreyi Coville. (2869, 2909)



357

Juncus alpinus insignis Fries.

Luzula campestris multiflora (Ehrh.) Celak. (3046) Wood Rush

Liliaceae. Lily Family.

Tofieldia glutinosa (Michx.) Pers. (2789, 2846, 2912) False As-

phodel
Allium cernuum Roth. (2895) Nodding Onion
Lilium canadense L. (2828) Wild Yellow Lily

Lilium philadelphicimi andinum (Nutt.) Ker. (2764, 2777, 2793,
2807, 2947, 2933) Wood Lily

Asparagus officinalis L. (3023) Asparagus
Smilacina stellata (L.) Desf. (2492) False Solomon's Seal

Maianthemimi canadense Desf. (2484, 2488) One-leaved Solomon's
Seal

Polygonatum biflorum (Walt.) Ell. Small Solomon's Seal

Polygonatum commutatum (R. & S.) Dietr. (3025) Great Solomon's
Seal

Aletris farinosa L. (2748, 2835) Colic Root
Smilax ecirrhata (Engelm.) Watson. Carrion Flower
Smilax hispida Muhl. Green Brier

Dioscoreaceae. Yam Family.

Dioscorea paniculata Michx. (31 13) Yam

Amaryllidaceae. .Amaryllis Family.

Hypoxis hirsuta (L.) Coville. (2519) Star Grass

Iridaceae. Iris Family.

Iris versicolor L. (2521) Iris

Sisyrinchium sp. ? (2485, 2514, 2855, 3018) Blue-eyed Grass

Orchidaceae. Orchid Family.

Cypripedium hirsutum Mill. (C. reginae Walt.) (2961) Showy
Lady's Slipper

Habenaria hyperborea (L.) R. Br.

Habenaria dilatata (Pursh) A. Gray. (2753, 2797)
Habenaria clavellata (Michx.) Spreng. (2884)
Habenaria leucophaea (Nutt.) A. Gray. (2800,2840) White Fringed

Orchid

Habenaria psycodes (L.) Sw. (3176, 3182) Purple Fringed Orchid
Pogonia ophioglossoides (L.) Ker. (2754, 2804)
Calopogon pulchellus (Sw.) R. Br. (2747)



358

Spiranthes cernua (L.) Richard. (2992, 2971) Ladies' Tresses

Liparis loeselii (L.) Richard. (2507) Twayblade

Salicaceae. Willow Family.

Salix amygdaloides Anders. (3172, 3175) Peach-leaved Willow
Salix lucida Muhl. (2900, 3060, 3170) Shining Willow
Salix serissima (Bailey) Fernald. (2995) Autumn Willow
Salix longifolia Muhl. (3080) Sand-bar Willow
Salix cordata Muhl.
Salix glaucophylla Bebb. (3033, 3036)
Salix syrticola Fernald. (2459, 3156)
Salix pedicellaris Pursh. (3174)
Salix discolor Muhl. Pussy Willow
Salix Candida Flnegge. (2758) Hoary Willow
Populus tremuloides Michaux. (3104) Trembling Aspen
Populus candicans Alton. (2780, 3155) Balm of Gilead

Populus deltoides Marsh. (3035) Cottonwood

Juglandaceae. Walnut Family.

Juglans nigra L. (31 17) Black Walnut
Carya ovata (Mill.) K. Koch. (3120) Shag-bark Hickory

Betulaceae. Birch Family.

Betula alba papyri fera (Marsh.) Spach. (3097) White Birch

Betula pumila L. (2493, 2500, 2813) Swamp Birch

Fagaceae. Beech Family.

Quercus alba L- (3125) White Oak
Quercus macrocarpa Michaux. (31 19) Bur Oak
Quercus velutina Lam. (2981) Black Oak

Santalaceae. Sandalwood Family.

Comandra umbellata (L.) Nutt. (2790) Bastard Toad-flax

Polygonaceae. Buckwheat Family.

Rumex britannica L. (3231) Great Water Dock
Rumex acetosella L. (3063) Sheep Sorrel

Rumex crispus L- (3095) Curled Dock
Polygonum tenue Micliaux. (3206) Smartweed
Polygonum lapathifolium L. (= P. incarnatum Ell.) (3227)
Polygonum amphibium hartwrightii (A. Gray) Bissell. (3179)
Polygonum mulilenbergii (Meisn.) Wats. (3247)



359

Polygonimi peirtisylvanicum L. (3238)
Polygonum acre HBK. (3241)
Polgonum persicaria L. (3253) Lady's Thumb
Polygonum hydropiperoides Michaux. Mild Water Pepper

Chenopodiaceae. Goosefoot Family.

Cycloloma atriplicifolium (Spreng. ) Coulter. (2975) Winged Pig-

weed
Chenopodium album L- Lamb's Quarters

Corispermum hyssopifolium L. (3226) Bug-seed
Salsola kali tenui folia G. F. \V. Mey. (2974) Russian Thistle

Amaranthaceae. Amaranth Family.

Acnida tuberculata subnuda Wats. Water Hemp

Caryophyllaceae. Pink Family.

Arenaria striata Michaux. (2510) Sandwort
Silene antirrhina L. (2449) Sleepy Catchfly

Silene stellata (L. ) Alton f. (3267) Starry Campion

Ceratophyllaceae. Hornwort Family.

Ceratophyllmn demersum L. (Collected by Dr. H. A. Gleason.)

Nymphaeaceae. W^ater Lily Family.

Nymphaea advena Alton. (3015) Yellow Water Lily

Castalia tuberosa (Paine) Greene. (3204) White Water Lily

Ranunculaceae. Crowfoot Family.

Ranunculus aquatilis capillaceus DC. (Batrachium trichophyllum

Bosch) (3014) White Water Crowfoot
Ranunculus delphinifolius Torrey. Yellow Water Crowfoot
Ranunculus sceleratus L. Cursed Crowfoot
Ranunculus pennsylvanicus L. f. (3244) Bristly Crowfoot
Anemone cylindrica A. Gray. (2761) Anemone
Anemone virginiana L. (3140)
Anemone canadensis L. (3029)

Berberidaceae. Barberry Family.

Podophyllum peltatum L. (3056) May Apple

(Cruciferae) Brassicaceae. Mustard Family.

Draba caroliniana Walt. (2477)
Lepidium apetalum Willd. (3101) Peppergrass



360

Cakile edentula (Bigel.) Hook. (2976) Sea Rocket
Sisymbrium officinale leiocarpum DC. (3251) Hedge Mustard
Radicula palustris (L.) Moench. Water Cress
Arabis lyrata L. (251 1) Rock Cress

Droseraceae. Sundew Family.

Drosera rotundi folia L. (2803) Sundew

Crassulaceae. Orpine Family.

Penthorum sedoides L. (3248) Ditch Stonecrop

Saxifragaceae. Saxifrage Family.

Heuchera hispida Pursh. (1663,2451) Alum Root
Parnassia caroliniana Michaux. (2959) Grass of Parnassus

Rosaceae. Rose Family.

Spiraea salicifolia L. (2888) Spiraea

Pirus mains L. (Malus mains (L.) Britton) Apple
Crataegus punctata Jaccj. (31 10) Thorn Apple
Fragaria virginiana Duchesne. (2455, 2480, 2773) Strawberry
Potentilla arguta Pursh. (2829)
Potentilla palustris (L.) Scop. (Comarum palustre L.) (3178)

Marsh Five-finger

Potentilla fruticosa L. (Dasiphora fruticosa (L.) Rydb.) (2853,

2973) Shrubby Cinque foil

Potentilla anserina L. (Argentina anserina (L.) Rydb.) (2518, 2924
Silver Weed

Geum canadense Jacq. (3107) Avens
Rubus occidentalis L. Black Raspberry

Agrimonia gryposepala Wallr. (3278) Agrimony
Rosa blanda Aiton. (3262) Smooth Wild Rose
Rosa Carolina L. Swamp Wild Rose

Rosa humilis Marsh. (3167)
Prunus serotina Ehrh. (3028) Black Cherry

Prunus virginiana L- (3024) Choke Cherry

Prunus pumila L. (2458, 2745) Sand Cherry

Leguminosae. Pulse Family.

Baptisia leucantha Torn & Gray. (2750) False Indigo

Lupinus perennis L. (2452) Wild Lupine
Tri folium pratense L. Red Clover

Tri folium repens L- White Clover



361

Trifolium hybridum L. Alsike Clover

Melilotus alba Desr. White Sweet Clover

Amorpha canescens Piirsh. (2894) Lead Plant

Petalostemum purinireum (Vent.) Rydb. (2872) Purple Prairie

Clover

Petalostemum purpureum f. arenarium Gates, forma nova (2922)
Sand-Prairie Clover

Petalostemum candidum Michaux. (2832, 2871) White Prairie

Clover

Astragalus canadensis L. (3042) Milk Vetch
Desmodium illinoense A. Gray. Tick Trefoil

Lespedeza capitata Michaux. (2962) Bush Clover

Vicia americana Muhl. Vetch
Lathyrus palustris myrtifolius (Muhl.) A. Gray. (2822) Vetchling

Lathyrus maritimus (L. ) Bigel. (3157) Beach Pea
Lathyrus venosus Muhl. (3016)
Apios tuberosa Moench. (2946) Wild Bean
Amphicarpa monoica (L.) Ell. Hog Peanut

Linaceae. Flax Family.

Linum virginianum L. (2833, 2845) Flax

Linum sp.

Oxalidaceae. Wood Sorrel Family.

Oxalis stricta L. (3230) Wood Sorrel

Geraniaceae. Geranium Family.

Geranium maculatum L. (3044) Wild Geranium
Geranium carolinianum L. (3152)

Rutaceae. Rue Family.

Ptelea trifoliata L. (3229) Hop Tree

Polygalaceae. Milkwort Family.

Polygala polygama Walt. (2768) Milkwort

Polygala sangiiinea L. (2948)
Polygala verticillata L. (2883)

Euphorbiaceae. Spurge Family.

Euphorbia polgA'goni folia L. (2967) Seaside Spurge

Euphorbia maculata L. (3258) Milk Purslane

Euphorbia corollata L. (2852, 2892) Flowering Spurge



362

Anacardiaceae. Cashew Family.

Rhus typhina L. Staghorn Sumac
Rhus toxicodendron L. (-506, 2805) Poison Ivy
Rhus toxicodendron radicans (L.) Torrey. Chnibing Poison Ivy

Celastraceae. Staff Tree Family.

Celastrus scandens L. Bittersweet

Aceraceae. Maple Family.

Acer negundo L. Box Elder

Balsaminaceae. Touch-me-not Family.

Impatiens biflora Walt. (2968) Spotted Touch-me-not

Rhamnaceae. Buckthorn Family.

Rhamnus alnifolia L'Her. (2486) Buckthorn

Ceanothus americanus L. (3162) New Jersey Tea
Ceanothus ovatus Desf. (1656, 2470, 2812) Red-root

Vitaceae. Vine Family.

Psedera quinque folia (L.) Greene. Virginia Creeper

Vitis vulpina L- (2930) River-bank Grape

Tiliaceae. Linden Family.

Tilia americana L. (3098) Basswood

Hypericaceae. St. John's-wort Family.

Hypericum kalmiaiumi L. (2462, 2844) Kalm's St. John's-wort

Hypericum sp.

Hypericum virginicum L. (Triadenum virginicum (L.) Raf.)

(2963) Marsh St. John's-wort

Cistaceae. Rockrose Family.

Helianthemum majus BSP (2752) Frostweed

Lechea villosa Ell. (2956) Pinweed
Lechea leggettii Britton & Hollick. (2889, 2932, 2953)

Violaceae. Violet Family.

Viola papilionacea Pursh. (2448) Violet

Viola sagittata Alton (=V. subsagittata Greene). (2481, 2839,

3161) Violet

i

i



363

Cactaceae. Cactus Family.

Opimtia rafinesquii Engelm. (2802) Prickly Pear

Lythraceae. Loosestrife Family.

Lythrum alatiim Pursh. (3159) Loosestrife

Onagraceae. Evening Primrose Family.

Ludvigia palustris (L.) Ell. (Isnardia palustris L.) (2898) Water
Purslane

Epilobium angnsti folium L. (2759) Fireweed
Epilobium densum Raf. (2989, 3236) Willow-herb
Oenothera biennis L. Evening Primrose
Oenothera rhombipetala Nutt. (3158)

Haloragidaceae. Water Milfoil Family.

Myriophyllum verticillatum L. Water Milfoil

Proserpinaca palustris L. (3215) Mermaid-weed

Araliaceae. Ginseng Family.

Aralia nudicaulis L. Wild Sarsaparilla

Umbelli ferae. Parsley Family.

Eryngium yuccifolium Michaux. (2886) Rattlesnake Master
Sanicula marilandica L. (3021) Black Snakeroot
Cicuta bulbifera L. (3234) Bulbiferous Water Hemlock
Cicuta maculata L. (311 1) Water Hemlock
Zizia aurea (L. ) Koch. (2476) Golden Alexanders
Heracleum lanatum Michaux. (3123) Cow Parsnip

Oxypolis rigidior (L.) Coulter & Rose. (2934) Cowbane

Cornaceae. Dogwood Family.

Cornus stolonifera Michaux. (2505, 2757, 3032) Red-osier Dogwood

Ericaceae. Heath Family.

Arctostaphylos uva-ursi (L.) Spreng. (2491) Bearberry

Primulaceae. Primrose Family.

Lysimachia thyrsiflora L. (Naumburgia thyrsiflora (L.) Duby)
(2520) Tufted Loosestrife

Steironema quadiflorum (Sims) Hitchcock. (2873)
Dodecatheon meadia L. (2450) Shooting Star



364

Gentianaceae. Gentian Family.

Gentiana crinita Froel. Fringed Gentian

Gentiana procera Holm. (2977, 2997, 3284, 3287) Small Fringed

Gentian

Gentiana andrewsii Griseb. (3271) Closed Gentian

Menyanthes trifoliata L- (3177) Buckbean

Apocynaceae. Dogbane Family.

Apocynnm androsaemi folium L- (31 14) Spreading Dogbane
Apocynum cannabinum hyper ici folium (Ait.) A.Gray. Indian Hemp

Asclepiadaceae. Milkweed Family.

Asclepias tuberosa L. (2781) Butterfly-weed

Asclepias purpurascens L. (2779) Purple Milkweed
Asclepias incarnata L. (2896) Swamp Milkweed
Ascelpias syriaca L- (3088) Common Milkweed
Ascelpias amplexicaulis Sm. (2746)
Acerates viridiflora Ell. Green Milkweed
Acerates viridiflora lanceolata (Ives) A. Gray. (2806, 2808) Sand

Green Milkweed

Con\'olvulaceae. Convolvulus Family.

Convolvulus sepium L- (3150) Hedge Bindweed

Polemoniaceae. Polemonium Family.

Phlox glaberrima L. (2791, 2837, 2991) Phlox

Phlox pilosa L. (2456) Phlox

Boraginaceae. Borage Family.

Lithospermum gmelini (Michx.) Hitchc. (2490, 2776) Puccoon

Lithospermum angustifolium Michaux. (1655, 3017) Puccoon

Verbenaceae. Vervain Family.

Verbena hastata L. (321 1) Blue Vervain

Labiatae. Mint Family.

Isanthus brachiatus (L.) BSP- (3242) False Pennyroyal

Scutellaria galericulata L. (2756) Skullcap

Scutellaria parvula Michaux. (2461) Small Skullcap

Nepeta cataria L. (3136) Catnip

Prunella vulgaris L. Self-heal



365

Monarda fistiilosa L. (3168) Wild Bergamot

Monarda mollis L.

Monarda punctata L. (2939) Horse Mint

Satureja glabra (Nutt.) Fernald. (2788,2861) Calamint

Pycnanthemum virginianum (L.) Durand & Jackson. (2874) Moun-

tain Mint

Lycopus sp. ? (3243)
Lycopus americanus Muhl. (2899, 2935) Water Horehound

Mentha arvensis canadensis (L.) Briquet. Mint

Solanaceae. Nightshade Family.

Solanum nigrum L- Common Nightshade
Physalis virginiana Mill. (2463) Ground Cherry

Scrophulariaceae. Figwort Family.

Verbascum thapus L. (3259) Mullen

Linaria vulgaris Hill. Butter and Eggs
Scrophularia leporella Bicknell. (3092) Figwort

Chelone glabra L. (3269) Turtlehead

Veronica virginica L. (2927) Culver's-root

Veronica anagallis-aquatica L. (3239) Water Speedwell

Gerardia pedicularia L. G^rardia

Gerardia grandiflora Benth.

Gerardia paupercula (A. Gray) Britton. (2970)
Gerardia skinneriana Wood. (2942, 2964)
Gerardia tenui folia Vahl. (3212) Slender Gerardia

Castilleja coccinea (L.) Spreng. (2479) Scarlet Painted Cup
Castilleja sessiliflora Pursh. (2466, 2751, 281 1) Painted Cup
Pedicularis canadensis L- (2496) Common Lousewort
Pedicularis lanceolata Michaux. (3235) Lousewort

Lentibulariaceae. Bladderwort Family.

Utricularia vulgaris americana A. Gray. (3180) Bladderwort

Utricularia cornuta Michaux. (2847)

Orobanchaceae. Broom-rape Family.

Orobanche fasciculata Nutt. (2482, 2487) Broom-rape

Bignoniaceae. Bignonia Family.

Catalpa speciosa Warder. (3169) Catalpa



366

Plantaginaceae. Plantain Family.

Plantago major L. Common Plantain

Plantago rugelii Dene.

Rubiaceae. Madder Family.

Galium boreale L. (2767) Northern Bedstraw
Galium trifidum L. (3237) Bedstraw
Cephalanthus occidentalis L. Buttonbush *

Caprifoliaceae. Honeysuckle Family.

Lonicera dioica L. (2453) Honeysuckle

Viburnum lentago L. (3094) Sweet Viburnum
Sambucus canadensis L. (31 16) Elder

Valerianaceae. Valerian Family.

Valeriana edulis ISTiitt. (1666) Valerian

Cucurbitaceae. Gourd Family.

Echinocystis lobata (Michx.) Torr. & Gray. Wild Cucumber

Campanulaceae. Bluebell Family.

Campanula aparinoides Pursh. (2885) Marsh Bluebell

Lobeliaceae. Lobelia Family.

Lobelia cardinalis L. (3214) Cardinal-flower

Lobelia siphilitica L. (2993) Great Lobelia

Loljelia spicata Lam. (2818) Spiked Lobelia

Lobelia kalmii L. (2919) Kalm's Lobelia

Compositae. Composite Family.

Vernonia fasciculata Michaux. (3213) Ironweed
Eupatorium purpureum maculatum (L.) Dark (2950) Jo-Pye Weed
Eupatorium perfoliatum L. (2951) Boneset

Liatris cylindracea Michaux. (2943) Blazing Star

Liatris scariosa Willd. (2958) Blazing Star

Liatris spicata (L. ) Willd. (2937, 2928) Blazing Star

Solidago speciosa Nutt. Goldenrod

Solidago speciosa angustata T. & G. (3265) Goldenrod

Solidago arguta Aiton. Goldenrod

Solidago nemoralis Aiton. (3273) Goldenrod

Solidago canadensis L. Goldenrod

J



367

Solidago serotina Ait. (2983, 3153)
Solidago rigida L.

Solidago ohioensis Riddell. (2988)
Solidago riddellii Frank.

Solidago gramini folia (L.) Salisb. (Euthamia graminifolia (L.

)

Nutt.) (3233)
Solidago spp.

Aster macrophyllus L. (3128) Aster

Aster novae-angliae L. (3263)
Aster sericeus Vent. (3154)
Aster azureus Lindl. (3268)
Aster ericoides L.

Aster multiflorus Ait. (3164)
Aster dumosus L. (3208, 3221)
Aster paniculatus Lam.
Aster, salicifolius Ait.

Aster umbellatiis Mill. (Doellingeria umbellata (Mill.) Nees) (2949)
Aster ptarmicoides T. & G. (2944, 2957)
Aster spp.

Erigeron philadelphicus L. (3020) Fleabane

Erigeron annuus (h.) Persoon. Daisy Fleabane

Erigeron ramosus (Walt.) BSP. (3090) Daisy Fleabane

Erigeron canadensis L. (Leptilon canadense (L.) Britton) (3256)
Horse-weed

Erigeron divaricatus Michx. (Eeptilon divaricatum Raf.) (3254)
Antennaria sp. Everlasting

Anaphalis margaritacea (L.) B. & H. (2990) Pearly Everlasting

Silpbium terebinthinaceum Jacq. (3216) Prairie Rosin-weed
Silpbium integrifolium Micbaux. (2893) Rosin-weed
Ambrosia artemisiaefolia L. (3274) Ragweed
Xanthium commune Britton. (3228) Cocklebvu"

Rudbeckia subtomentosa Pursb. (2890) Cone-flower

Rudbeckia hirta L. (2830) Black-eyed Susan
Lepachys pinnata (Vent.) T. & G. (2891) Cone-flower

Heliantbus occidentalis Riddell. (2965) Sunflower

Heliantbus occidentalis illinnensis (Gleason) Gates. (2774, 2887,

2936)
Heliantbus grosseserratus Martens
Heliantbus maximiliani Scbrad. (3282)
Heliantbus divaricatus L. (2954)
Heliantbus strumosus L.

Heliantbus spp.



368

Coreopsis lanceolata L. (2478) Tickseed

Coreopsis lanceolata villosa Michaux. (2817)
Coreopsis palmata Nuttall. (3148)
Bidens vulgata Greene. Stick-tight

Bidens trichosperma tenuiloba (A. Gray) Britton. (2982) Tickseed

Sunflower
Helenium autumnale L. (2984) Sneezeweed
Achillea millefolium L. (2760) Yarrow
Artemisia caudata Michaux. (2972) Wormwood
Cacalia tuberosa Nutt. (3249) Indian Plantain

Senecio balsamitae Muhl. (2512, 3031) Ragwort
Cirsium pitcheri (Torr.) T. & G. (2866) Pitcher's Thistle

Cirsium muticum Michaux. (2953) Swamp Thistle

Cirsium arvense (L. ) Scop. (3245) Canada Thistle

Krigia amplexicaulis Nutt. (2499) False Dandelion

Taraxacum erythrospermum Andrz. Red-seeded Dandelion

Lactuca canadensis h. Wild Lettuce

Prenanthes racemosa Michaux. (3283) Rattlesnake-root

Prenanthes alba L. White Rattlesnake-root

Hieracium canadense Miciiaux. (2945) Hawkweed
Hieracium aurantiacum L. (2826) Orange Hawkweed. Though not

occurring on the beach proper, but in the oak woods back of

tlie Glenwood ridge, this is inserted. here on account of the

extension of its westward limit.

The following additional plants, although they were found within

the limits of the region, were limited in distribution to the dump
heaps and railway ballast.

Abutilon theophrasti Medic. Velvet Leaf

Agropyron repens (L.) Beau v. Couch Grass

Amaranthus retroflexus L. Pigweed

Ambrosia psilostachya DC. Ragweed
Anthemis cotula L. Dog Fennel

Arctium minus Bernh. Burdock

Brassica arvensis (L.) Ktze. Mustard

Capsella bursa-pastoris (L.) Medic. Shepherd's Purse

Eragrostis purshii Schrad.

Erechtites hieracifolia (L.) Raf. Fireweed

Helianthus annuus L. Sunflower

Helianthus atrorubens L. (3219) Sunflower

Hordeum jubatum L. (3040) Squirrel-tail Grass

Lactuca pulchella (Pursh) DC. (3220) Blue Lettuce



369

Lactuca scariola L. Prickly Lettuce

Lithospemium officinale L. (2784) Puccoon
Melilotus officinalis (L.) Lam. Yellow Sweet Clover
Panicum miliaceum L. (3207) Millet

Polanisia graveolens Raf.

Polygonum orientale L. (3279) Prince's Feather

Polygonum aviculare L. Knotweed
Setaria glauca (L. ) Beauv. Yellow Foxtail Grass

Setaria viridis (L.) Beauv. Green Foxtail Grass

Sisymbrium officinale (L. ) Scop. (2819) Hedge Mustard
Solanum dulcamara L. (3086) Bittersweet

Sonchus oleraceus L. Sow Thistle

Stellaria aquatica (L.) Scop. (2820) Water Chickweed
Tanecetum vulgare L- Tansy



BIBLIOGEAPHY OF THE MORE IMPORTANT WORKS
CONSULTED

Adams, C. C.

1909. The ecological succession of birds. An ecological survey of

Isle Royal, Lake Superior, pp. 121- 154. (Published by the

Mich. State Biol. Surv. as part of the Rep. of the Board of

the Geol. Surv. for 1908.)

Clements, F. E.

1904. The development and structure of vegetation. Botanical

Survey of Nebraska, 7:3-175.
1905. Research methods in ecology. Lincoln, Nebraska.

Cowles, H. C.

1899. The ecological relations of the vegetation on the sand

dunes of Lake Michigan. Bot. Gaz. 27:95-117, 167-202, 281-

308, 361-391, /• i-^^-

1901. The physiographic ecology of Chicago and vicinity; a

study of the origin, development, and classification of plant

societies. Bot. Gaz. 31 : 73-108, 145-182, /. 7-55.

Drude, Oscar.

1889. Uber die Prinzipien in der Unterscheidung von Vegeta-

tionsformationen, erljiutert an der centraleuropiiischen Flora.

Engler's Jahrb., 11:21-51.

Engler, A.

1902. Die pflanzengeographische Gliederung Nordamerikas.

Notizbl. d. Konigl. Bot. Gart., .Appendix IX. (Map showing-

floral provinces.)

Gleason, H. A.

1910. The vegetation of the inland sand deposits of Illinois.

Bull. 111. State Lab. Nat. Hist. 9:23-174, pi. 1-20.

Goldthwait, J. W.
1907. The abandoned shore lines of eastern Wisconsin. Bull. 17,

Wis. Geol. and Nat. Hist. Surv.

1908. The records of the extinct lakes. Bull. 7, 111. State Geol.

Surv. : 54-68, pi. 6, 7, /. 50- 7<5.

Harper, R. M.
1906. A phytogeographical sketch of the Altamaha grit region

of the coastal plain of Georgia. Ann. N. Y. Acad. Sci. 17:

1-415, pi. 1-28, f. 1-17, map.



371

Harvey L. H.
1908. Floral succession in the prairie-grass formation of south-

eastern South Dakota. Bot. Gaz. 46:81-108, 277-298, /. i-j,

1-4.

Jaccard, P.

1902. Gesetze der Pflanzenvertheilung in der alpinen Region.

Flora 90: 349-377-

Jennings, O. E.

1908. An ecological classification of the vegetation of Cedar
Point. Ohio Nat. 8: 291-340, /. 1-22.

1909. A botanical survey of Presque Isle, Erie County, Penn-
sylvania. Ann. Carnegie Mus. 5 : 289-421, pi. 22-^1.

Kearney, T. H.
1900. The plant co\'ering of Ocracoke Island. Contrib. from

the U. S. National Herbarium 5 : no. 5.

Kihlman, A. O.

1890. Pflanzenbiologische Studien aus Russisch Lappland. Act.

Soc. Faun. Flor. Penn., 6.

Leverett, F.

1910. Outline of the history of the Great Lakes. 12th Report
Mich. Acad. Sci. : 19-42, with maps.

Livingston, B. E.

1903. The relation of soils to natural vegetation in Roscommon
and Crawford counties, Michigan. Ann. Rep. Geol. Surv.

Mich. 1903 : 1-30.

Olsson-Seffer, P.

1909. Relation of soil and vegetation on sandy sea shores. Bot.

Gaz. 47: 85-126, /. 1-12.

Pound, R., and Clements, F. E.

1898. The vegetation regions of the prairie province. Bot. Gaz.

25: 381-394, Pl- 21.

Sargent, C. S.

1884. Report on the forests of North America. U. S. Tenth
Census Report, 9. Maps.

Schimper, A. F. W.
1903. Plant geography upon a physiological basis. Oxford.

Transeau, E. N.

1903. On the geographic distribution and ecological relations

of the bog plant societies of northern North America. Bot.

Gaz. 36: 401-420, /. 7-5.



372

Warming, E.

1909. Oecology of plants. An introduction to the study of plant-

communities. Oxford.

Whitford, H. N.

1901. The genetic development of the forests of northern Mich-

igan; a study in physiographic ecology. Bot. Gaz. 31: 289-

325, /. 1-18.

ERRATA

Page 256, line 3 of table, for Dr. H. M. Pepoon read Dr. H. i". Pepoon.

Page 278, line 16, rhizomes should be in Roman type.

Page 315, line 10, for Apoeynutn read Apocynum.

Page 351, line 4 from bottom, for xerophilic read xerophy/ic.

Page 356, line 14 from bottom, for Symlocarpus read Syinplocarpus.

Page 365, line 14, for tliapiu read ihapsus.

Plate XXXIX, for Calamogroslis read Ca/amagrostis.

Plate LIV, exchange places of cuts, but not the legends.



Plate XXXVII.

i.AKK 11

(^.III futl 3*-

^|...i..U ., ,

;
.' K >

wiiiii.i-..|.n

r in X

>! I?.
pi;;"' ,

;

i?n: -ly.

x;

1 'r^:.

I.l -,.I,„.-,l,*l.,l,..\.a.*;..l,.,.\.i.J

' ir.nin.iiiki.

K,

--Ib-im^ /

;

_Ii
WAiK k*;an

J*,.

General map of the southern part of the Beach area.



Plate XXXVIII.

General map of tlie northern part of the Beach area.



RIVER.

1
Plankton Assoc.

i
Ohara Assoc

1 :yPotamogeton Assoc.

OASTALIA-NY)ffHAEA ASSOC?

OC.

JTTARIA ASSOC.

I

1 i

Ranunculus aquatllls
caplllaceus Assoc.

OAREX ASSOC.

1
PHRAGMITES-TVPHA ASSOC.

\

ASSOC.V /'^OsmiindE

i /

SCIRPUS VALIDUS ASSOC.

i
SCIRPUS AMERICAJJUS ASSOC.

i
-OLADIUU ASSOC.

INADENSIS

[S

CA PRAIRIE ASSOC

a Assoc.

I showing the successions exhibited between

associations in the Beach Area, Illinois,

primary successions.

secondary successions due to clearing,

burning or other disturbing factors.

letters denote the important associations.



I'l.ATK XXXIX.

. LAKK MICHIGAN.

LOWER BEACH
i

CjkKILE-XANTHIUM ASSOC

\AwnpMla Dune. /

OALAMOVILPA DUNE

i
Prunus puDilla

Dune.

i ,Populus ca: id leans
Dune

VELUTINA ASSf^C.

i
QUERCUS-CARYA ASSOC.

X
ULMUS-ACER ASSOC.

i
ACER SACCHARUM ASSOC.

Lenna-Riccla Assoc.

MENYANTHES-SACITTARIA ASSOC,

RIVER.

i
Plankton Assoc./

Ohara Assoc.'' .

1 /Potamogeton Assoc

OASTALlA-NYlffHAEA ASSOC?

\Ranunculus aquatllls
oaplllaoeus Assoc.

1
OAREX ASSOC.

PHRAGMITES-T rPHA ASSOC.

\
SOIRPUS VALIDUS ASSOC.

SOIRPUS AMERICAHUS ASSOC.

CLADIUU ASSOC.

OALAMOGROSTIS CAMADENSIS
ASSOC.

I

IRIS ASSOC."*^ / 'Osmunda Assoc.

1
LIATRIS SPICATA PRAIRIE ASSOC

Diagram showing the successions exhibited between

the plant associations In the Beach Area, Illinois.

primary successions.

secondary successions due to clearing,

burning or other disturbing factors.

Capital letters denote the important associations.



Pl.ATE XL.

Wind direction; sunshiiiu ami temperature curves for
Chicago and Milwaukee.



Plate XLL

/^'amhc-r' pf- %ys [^fTf^ 0-0/, or )ri

V S f

4 i : lAAe-o-JTT, 7=*r4c//3LtV t.,/o ^.faf^r^..

Mean precipitation for Chlcayo ami Milwaukee, by motitlis,
for thirty-six years.



Plate XLII.

Mi^an snowfall, by months, for Chicago (19 years) and
Milwaukee (3b years).



Plate XLIII.

3.



Plate XLIV.

,, ',e^^\-<^

Fig-. 1. An oak ridge tiear Kenosha, Wis., which is being washed awav by Lake Michigan.
November 23, 1909.

Kit.'. 2. Beach jjool near Waukegan, Illinois, showing sanderlings feeding-. August 17, I'WJ.



Plate XLV.

Fig-. 1. Little dunes formed by seaside spurye
{Euphorbia polygonifolia). Beach, Illitiois. Aug-ust
30, IWI.

-r<

—

3andplain

Section of Beach
upon which Lake
Michigan is "beginning
an attack.

111. -Wia. Stat© line
Sapt 1909.

Potentilla

anserina

Association

Juncus
"balticus

littoral is
Association

Beach

L ," Potentilla
-^ndp^.-^in ansc-rina

Juncus baltlcua llttoralis
Relic Dune.

sand-

plain

Scatterlnj;

plants or

Euphorbia
poly^anl folia

Xanthiura coianune
i'otentilla, etc.

•1<y ic Dune

I

Old
Bldff
Line.

Bird '3 eye view nr hemrh

Lake

liichigan

Fig". 2. Diagrams illustrating the character of the shore south
of Kenosha, Wisconsin, September, I'lCKi.



PI.ATE XLVI.

Fiff 1 Relic dunes along- the shoreof Lake Michigan nearKenosha, Wisconsin. A closer

view of "A" is shown in Fig-. 2. "C" is a nearly extinct relic dune, and "D" is a Jiiiiiperus

relic dune. With the exception of "D" the relic dunes shown are formed by Junciis ballicus

/ittoralis. August 30, IWO.

X3'^^•^H^

Fiif. 2. Juiicun iHillinis liltonilis relic dune, near Kcnnslia, Wisconsin. Novi-mber 2.i, IW).



Plate XLVII.

%

ft^^

Fig-. 1- A relic dune near Kenosha, Wisconsin, sliowing- the disruptive power of freezing-
water. November 23, 190P.

Fig. 2- Calamovilfa longifoHa dune at Beach, Illinois. July 1^'. I'JO''.



Plate XLVIIT.

Figr. 1- Bluff at Camp I^ogan, Illinois, beinp cut by Lake Michig-an, showing- exposed
roots of Calamoviifa longifoliu on the left, and of red-osier dog^wood {Cor/ms stolonifera) on the
rig-ht. September 4, 1%^".

I'"ig-. 2. Part of the beach near Hearh, Illinois, showinff an Ammophila dune in the
foreground, a .Salix gUim ophylla duiit- on the right, and, in the center of tlie background,
a Populus candicans dune. September 11, IQCH'.



Plate XLIX.



Plate L.

-*
W^\

Fig- 1. Sporobo/rts crypta/idrnSt illustrating- growtli habit. Winlhrop Harbor, Illinoi:
Au^^ust 3U, 1409.

FiR'. 2. Andropoeon scoparius buncli-nrass prairie near Beach, Illinois.
August 17,1909.



Plate LI.

Tig-. 1. Growth hahit oi Peia/osie/Hum piirpureum i. arenarmm in the bunch-grass prairie,
Waukeg-an, Illinois. Aug-ust 13. l^tlO.

Pig-. 2. Blowout i a the oak (^«£rt-«j 7'^/K//«rt) association near Beach, Illinois. Reveg-e-
tation consists largely of heath plants, but scattered throughout are oak seedling's. Julv 19,
1909.

" K . ,



PLATr; LII.

Fij^. 1. Heath near Heach. Illinois. 'Juniperus horizontalis in the foreground. Back of a
strip of sand is bearberry (Arclosia/'fivios uva-ursi) In the backg-round is a tree of white pine
{Piuiis strobus) and a grove of black oak ( i^uerrus velutina). August 24, 190*J.

Pis'. 2. Blowout in tiie heath. Zioti Citv, IlliiKjis. Revegetatioti mainly by h(?ath plants.
September 4, 1909.



Plate LIII.

Kijr. I. Blowout on the edge of the oak {^lu-rLiis rcliitinn) near Beach, Illinois. Reveg-etation

by prairie, marsh, and thicket plants. September 11, 10(W.

Fig-. 2. Marsh associations in the Dead River near Beach, Illinois. Yellow water-lil.v(Arw-

pliata advcna), arrowleaf (Sagiltaria lali/olia), cattail (Typlut latifolia), and reed (Phragmltcs

communis'), A-Ugusl 13. 1910.



Plate LIV.

Fig-. I, Scirpus amcrkaHus (3-anyled bulrusb) associalioii toward tlu* left hand side.

Scirpns validns (g-iant bulrush) association at the rig'ht of the center. Bt-ach, Illinois. Auyust
24, 1009.

Figr. 2. Swale south of Beach, Illinois^ dominated by ClaJium mariscoidts.
background. September 11, V'OO.

Pines in the



Plate LV.

Fig'. 1. A swale near Zioii City. Illinois, sliowing- the Calamagrostis canadensis association
in the foreground and an aspen-willow grove in the background, separated bv a narrow zone
of shrubs. September 4, 1^)09.



Plate LVI.

Fig-. 1. Blazing- star {Liatns spicata) prairie. Zton City, Illinois
cajtdicans) in the background. September 4, 1909.

Balm of Gilead {Populns

Fig-. Z The prairie invading- the pines,
alive while no seedlings are present. Beach, Illinois

One of the last stag-es, showin^j old iri-es scarcely
June 22, 1909.