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UPON PARASITIC FUNGI. 

BY T. J, BURRILL, 

(Professor of Botany and Horticulture in the Illinois Industrial University.) 

Many doubt the action of microscopic fungi in causing diseases of 
higher plants and animals. Indeed it has only been in our century, and 
mostly in the latter part of it, that botanists have distinguished these 
minute parasites as independent plants. Schleiden (1) in a work written 
about 1845 said, " I cannot regard the true Uredines, etc., ( Coniomycetes) 
as independent plants. Meyen \2) observed the formation of Uredo mnidis 
as an abnormal process of cell formation in the interior of the cells of the 
parent plant; and, in this respect, my own observations on Elyrnus arena­
rius coincide with his." Unger (3) in 1833 sought to prove that the so-called 
fungi were changed conditions of diseased tissues; and Fries in a classic 
work upon fungi, holds similar views. 

But the matter is not left undecided The improvements in micro-
scopes, and in methods of tracing the life history of low organisms, have for­
ever settled the doubts in the minds of scientific men. Nothing can be more 
satisfactory in the way of evidence, than to see with one's own eyes the spores 
germinating, penetrating the plant tissues, and in due time producing again 
spores like the ( riginal ones. This has been done again and again, and may 
be seen by any one who will take the trouble to follow, day by day, the de­
velopment of any of the hundreds always and everywhere at hand. Their 

I. Principles of Scientific Botany. London, 1849, p. 151.
2. U eber die Entwickelung des Getreidebrandes in der l\'lais-Pflanzen, Weig-

mans Archiev., 1837, p. 419. 
3. Die Exantheme des Pflanzen, Wein, 1833, p. 356.



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eflfects, likewise, may thus be observed, obliging the most skeptical to admit

the agency of the parasites in causing the malady to which attention is given.

Probably Prevost first discovered the fact, that the spores of fungi

germinate. This was in the first decade of our century. Since then many
eminent naturalists have given abundant testimony as to the true parasitism

of species, and of their individuality as such. We may, without disparag-

ment to others, mention the names of Leville (4), Tulasne (5), Berkeley (6),

and M. Bary (7) as authorities, whose writings have conclusively

established the fact that these parasites do cause the maladies attrib-

uted to them. Robin (8) and Leidy (U) have published prominent treaties

on the vegetable parasites upon living animals.

Observers in this field are now much more numerous than ever before

and, having the advantage of the former contributions, are gaining rapidly

in the kaowledge of kinds and of the injuries caused by these small but in

no wise insignificant organisms. Preventives and cures naturally follow

investigations of cause. They certainly cannot precede the latter except

by accident ; hence, if any one feels like asking " What use ? " let him
possess himself in patience ;—in the coming time, man wall assert his

dominion here as well as elsewhere over the natural world. Something has

already been done. The vine disease in Europe has been kept down by the

use of sulphur, as are the rose and verbena mildews in green-houses. Some-
times prevention is attained by removing promptly attacked parts, as in the

case of the peach-rot, and, as further detailed below, sometimes by destroy-

ing the spores of the fungus, as in the bunt of wheat. Cultivators now often

unconsciously scatter the germs and ignorantly provide ways and means for

their development. The march or migration of a parasite of this kind is

sometimes as well marked as that of an injurious species of insect.

Purcinin malvdcearum, Monf., affecting cultivated hollyhocks, has been

traced from South America through the United States to England and thence

to the continent as certainly as the Colorado potato beetle has across our

territory. Timely, intelligent action in such cases might avert great disas-

ter. Had this fungus attacked the cotton plant, as it was feared it would,

what estimate could be placed upon the loss ! What money- value is de-

stroyed iuour own state hy rust {Ftu-cinid (/ramiin.'i, Pets.) on wheat, oats, etc.;

what discouraging losses by the multitudinous blights upon our cultivated

crops, many of which are known, and others supposed to be, caused by para-

sitic fungi I

4. Amiales des Sc. Naturelles. 1839, etc.; and •'Mycologie," and "Uredines,"
m Diet. d'Hist. Nat., par D'Orbigny.

5. Annales des Sc. Naturelles, 3 ser., tome VII, 1847 ; 4 ser., tome II, 18r)4._

6. Introduction to Crj-ptogamic Botany, London, 1857, p. 261. Outlines of

British Fungology, London, 1860, p. 68.

7. Ueber der Brandpilze, 1853. Morphologie und Physiologic der Pilze, 1866,

and many papers in Annales des Sciences Naturelles and elsewhere.

8. Historie Naturelle des Vegetaux Parasites qui croissent sur rhomme et sur

les animaux vivants, par Charles Robin, Paris, 1853.

9. A Flora and Fauna Within Living Animals, by Joseph Leidy, Smithsonian

Cont. to Knowl.. Vol. 5, 1853.



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Aside from what may be called the practical value of the study, in-

cluding that which leads to the better understanding of the higher forms of

living things, these microscopic creations have many attractions for the stu-

dent. Nature is always, and to every one, interesting
;.
her pursuit is alluring

in the highest degree. To see rare forms men traverse oceans and make pil-

grimages over continents ; but here are countless unseen living things,

under our feet, on every side, in the air we breathe, in the food we eat, on

plants, on animals, germinating and propagating under our own finger nails

and even in our mouths, possessing a variety of form and structure, often

curious and beautiful, never equalled by art and not surpassed in nature.

Their wonderful life-histories stimulate inquiry, engage and enchain the

attention. He who possesses a microscope, with the ability and opportunity

to use it, need never wander from his own door to find an abundance of

material awaiting his researches, and entertaining and instructive biogra-

phies ready for his pursuit. (10.)

The Peronospori^. (11). Among the pests to the cultivators of fields

and gardens, the members of this family maintain a bad pre-eminence.

None have attracted more attention from the injuries they do to important

plants, and from their peculiar and interesting life-history. Formerly
classed in widely different groups on account of their difference in structure,

the species have been united from their agreement in development. All

produce conidia,—naked spores borne upon the tips of erect filaments or

/iT/phse,—which in some cases germinate directly and sometimes give origin

to some half-dozen zoospores. The latter are small, more or less globular

bodies, capable of rapid movements in water by means of two long cilia,

which they lash from side to side with astonishing rapidity. They thus

swim in a drop of rain or dew some minutes or hours ; then, losing the pro-

pelling hairs, settle down, and under favorable circumstances germinate like

the conidia by protruding one or more slender tubes, which penetrate the

tissues of the supporting plant and become the myceliutn or vegetative

threads of the fungus. Besides, through the conidia and their offspring,

the zoospores, these particular plants have another method of reproduction.

The term oospore has been given to a fruit-body found to arise from the

conjoined action of two separate cells of the mycelium. This is a sexual

process well known among the algse or sea-weeds, but not yet well made out

in most fungi, and analogous to the production of seed in flowering plants

by the united action of stamen and pistil. The cell producing the oospore

is called a gonosphere or oogonium^ and its partner an antheridium. The
oospores are found on or in the tissues of the host, sometimes only upon
one of several plants that the conidia are found upon. Unlike the latter,

they lie dormant for some months, but, like them, finally give origin to

10. Cooke's little book on Rust, Smut, Mildew and Mould is an excellent one
for a beginner.

11. The plants enumerated in this paper are from collections made by the
author between September 21st and and October 16th, 1876, mostly from the area
of ground upon which he makes his home. Any collector will perceive that more
of the Uredines and other families are omitted than are mentioned.



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zoospore3 which appear identical with those produced by the conidia. The
office of the oospore appears to be to pass the winter. The family consists

of two genera, Peronospora and Cj/stujms. The species of tlie former have

the appearance of moulds, producing conidia singly or in clusters at the

tips of the fertile threads, while those of the latter occur as white pustules

on leaves, bearing the conidia in moniliform strings, the fertile hyphae or

threads having no prominence. Generally the mycelium of both has curious

processes, termed hmipforia, penetrating the cells of the supporting plant,

as shown in Plate II, Fig 7. The threads themselves, when first emitted

from the spore as well as w'hen buried and ramified in the tissues, often pen-

etrate the cell through and through, being found at considerable distances

from the diseased-looking spots upon which the fruiting threads appear.

Over forty species of Peronospora have been described, of which only

six are known to exist in the United States. Many others probably await

the researches of botanists. Of the six, three, by far the most common
ones, are in the present described collection.

Feronospora infestiuis, Mont., (^Plate II, Fig. 8.) Very common on
potatoes and tomatoes. It has also been found on Bittersweet (Solanum
dulcamara), and even upon a not closely related plant, Anthoccris viscosa{l'i)

belonging to the Scrophulariacesc. This is by far the most famous, or in-

famous, of the species of this genus, causing the well known and often

dreaded potato rot. Its history has been often toldll^J), but a new chapter

was added last year by Worthington Gr. Smith (14), of England. Previously

the oospores had not been found as such, and so much search had been
made for them that it was quite generally believed that they must exist

upon some other supporting plant. Clover, among others, was suspected.

The finding of them in the tissues of the leaves and stalks of the potato

settled the doubt and bids growers beware of leaving the old potato top to

breed the pestilence another year.

P. gavglifonnis. Berk, {Plate II, Fig. 3.) Common on lettuce and
some allied compositse {Lactuca altissima and Nahalus alius. Farlow.)
Zoospores not observed. Conidia germinating and penetrating young
leaves, the tissues usually decaying from above downward until the whole
plant is involved and becomes a slushy, putrescent mass. This parasite is

especially destructive in forcing-houses. Several hundred dollars worth of

lettuce was lost by one propagator here last winter from this fungus (l-'^>).

The only cure now known is to keep the atmosphere as dry as practicable

and remove very carefully the diseased leaves.

P. iiticola, B. & C. {Plate II., Figs. 6 & 7.) Common on grape
leaves, and becoming very destructive in this vicinity, worse apparently

12. Farlow, Synopsis of the Peronosporeae of the United States, Bulletin of
the Bussey Institution, p. 426.

13. Smith, Ohio kg. Report. 1872, Essays, etc., p. 20.

14. Farlow, Gardener's Monthly, Nov. 1875, p. 274. Smith, Ohio kg. Report,
1862, Essays, etc., p 20.

15. Smith, Gardener's Chronicle, July 17, 1875, p. 69. Quarterly Journal of
Microscopic Science, October, 1875.

16. Farlow on the American Grape Vine Disease. Bulletin Bussey Institution.

p. 415.



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upon the smooth-leaf varieties. The Clintons were nearly or quite killed

by it the last two summers. This seems to be a native American, and has

often been mistaken for Erijiiiphe tuckeri^ Berk^ which constitutes the

vine disease in Europe,—a mistake which has led to an error and disap-

pointment in its treatment. Sulphur proves effectual in case of the Erydphe,

but it lives upon the surface of the leaf, not in the tissues, as does our

plant. Notwithstanding the continued failures, cultivators still are known
who spend their time and money with the sulphur remedy, showing again

the importance of the knowledge of the species and their habits. But, un-

fortunately, a practicable remedy is not now known. The condia produce

zoospores, which swim in water some fifteen minutes, then germinate. The
oospores are found among the cells of the leaf in autumn. If all the old

diseased leaves could be burned, a preventive would be attained.

During the last winter (1874-5) a parasite (Plate I, Figs. 5, 6, 7, 8, 9,

10, 11) was noticed upon many of the plants in the green-house belonging

! ) ihe Illinois Industrial University. A few of the diseased leaves being

taken home for examination, although they were exposed but a few minutes

in a room with previously healthy window plants, the same disease soon ap-

peared upon the latter ;—a case of the unwitting distribution of disease

germs by man. Our real study of this species commenced, however, in

October, 1876, when it reappeared in both the localities just named. In

one case a box of earth in which some affected plants grew last year ( winter

of '75-6) was left dry during the summer and some healthy plants

replaced in the box in October, 1876. Every care practicable was
taken to see that these plants were sound and to exclude infection from

any other source. In a week's time there was evidence in abundance

of the same parasite. The conidia are now known to germinate when
at least one month old, but did they lie dormant all summer? Sup-

posed oospores were found in the petals of Salvias, and figured (Plate

I. Fig. 10.) This body is 1-500 in. in diameter, with an apparent hyaline

reticulated epispore and a yellowish included spheroid. The fertile hyphae

are dingy or smoky colored, torulose when dry, septate, simple or branched,

bearmg conidia in dense clusters on the sides and tips of the rigid, blunt

extremities. Conidia oval, pappillate, slightly tinted, 1-1800 by 1-2660 in.

Believing the plant to be an undescribed Feronospora, it was christened P.

fumosa ; but later examination, since the figure was made, makes it question-

able about the so-called oospore being such. If not, the plant may belong

to the aforetime related genus Foltactis, Link, in which case its parasitism

on living plants is an anomaly. The conidia germinate in water, often emit-

ing two or three tubes. Zoospores not seen. On the leaf the germinating

tubes run over the surface or penetrate through the cells to the interior.

In about five days from the sowing, the fertile hyphae appear with their

conidia. They arise from the stomata or from the external mycelium.
Sometimes the conidial hyphse do not appear until the leaf or young stem is

in an advanced state of decay. On some plants only unhealthy or fallen

leaves appear to be affected. Salvias, G-eraniums, Centaureas, Senecios and
others of diverse orders suffer from its attacks, while as many as twenty

kinds have been found living or dead with the fungus upon them. Had time



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permitted, I should have been glad to submit this plant to the inspection of

others before, perhaps, thus exposing my own incapacity. The only similar

figure which I have seen is in Schleiden's Principles of Scientific Botany,
London, 1849. Plate '2, Fig. 8. This cannot be the plant.

Of the four recorded United States species of Ci/sfopns, three were
found. These are exceedingly common on the plants indicated. They do

not, however, have the blighting eifect of the Peronosporioe. Plants thor-

oughly dotted with their pustules appeared to survive without great injury.

Their microscopic character is so well known to botanists that nothing

would have been gained by selecting new specimens to figure, so in my haste

copies were selected as indicated. The other figures are from the collec-

tion, but none of the plants are more common than these.

Cystopus candidus, Lev.^ {Plate I, Figs. 1, 2, 3^ 4.) Common on cru-

ciferous plants, notably here on horse radish and cabbage.

C. cubicus, Mart. On Ambrosia artemisiscfolia , i\iQ common xdig weed.

C. bliti, Bivon. On Portv.laca oleracea (purslane) and Amaranthus
retrojiexus.

Perisporiacei. Notwithstanding the similarity of the names of these

families, the plants are very diff'erent, as a glance at the plates will show.

They, however, agree in their injuries to living plants, constituting very

many of the leaf blights of this and other countries. Some of them are

most exquisitely beautiful under the magnifier, a thing which the disciples

of the development theory of species have not yet accounted for. Their

beauty surely does not come from natural or sexual selection. The myce-
lium runs over the surface of the leaves, never appearing to enter the cel-

lular structure, yet, in some way, deriving nourishment from it. Here
applications, as of sulphur, have direct eff'ect. Here, too, the vine and the

hop mildews belong. Conidia are borne in moniliform strings arising from

the mycelium. The two together often give the aflected leaves a dusty,

whitened appearance, as if coated with whitewash. Later the spherical

bodies

—

conceptades^oi dark color, as represented in the plates, are

formed, sometimes exceedingly numerous, sometimes few and hard to find.

The conceptacles have not yet been discovered in the vine disease of Europe.

These conceptacles have at length radiating oppendafies, difi'erent from the

mycelium, of many different forms, though constant within narrow limits in

a given species. Inside the usually reticulated conceptacles there are

attached to the base one or more sporangia or spore-sacks. These are thin

and transparent, showing plainly the few or many spores. Sometimes, in-

stead of sporangia, multitudes of naked and smaller spore-like forms are

found ; and sometimes similar ones are contained in a stalked flask-shaped

or urn-shaped vessel, as seen in Plate III, Fig. 7. Still other apparent

fruit-bodies are found on the mycelium or the appendages of the conceptacles.

I do not remember seeing these described, but have often met them and am
fully convinced that they belong to the same plants. They are dark-

colored like the Dematiei species, and of the forms shown in Plate III, Figs.

2b, 2c, 2d, 7f, and Plate IV, Fig. 12. Save in quantity, they are not

unlike forms of the black mildews found on thick-leaved plants and known



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under the na'iies fnmarfo, Ant'nnaria. Capnodium, etc., but their positive

connection with these plants, positive at least in the case of the specimen

figured in Plate III, Fig 2, of course destroys any sort of specific individu-

ality. I cannot say that they are reproductive bodies, but they certainly

look like it. Other plants not distantly related have such forms of fruit.

It is probable that the conceptacle, v?ith its contained sporangia, in all these

plants, is the result of a peculiar union of specialized cells (17), as in the

Perono-porise.

Sphperotheca caMagnei, Lev. On Taruxicum, Hop, Spirea, etc. To
this species we refer with doubt the plant figured on Plate III, Fig 3,

found on Ererhfites hleraxifoUus, but the conceptacle is larger (1-245 in.)

and the mycelium denser than in any undoubted plants of the species no-

ticed, and the appendages somewhat diiferent. Instead, too, of being dis-

tributed over the plant, this is found almost entirely upon the stems and
iiuder sides of the leaves, in patches. Appendages (of which there are one

to three ) colored to a septum. Sporangium one, spores eight, oval, 1-8000

by 1-4300 in.

PhyVnctinia gtittata, Lev., (Plate IV, Pig. 6.) Common on Fraxinus

viridis. This species is reported to be common on Quercus, Carpinus, Ber-

beris, Alnus, (Jorylus, etc.

Podo^plioera kunzei (?), Lev. {Plate III, Fig. 2.) On cultivated

cherry. This is almost surely not kunzei, Lev., but it is the nearest to it

of any I know and I am loth to call it new, since so conspicuous and mjurious

a species could hardly have escaped attention. Leaves of all varieties of

cultivated cherries were distorted and caused to fall, from the middle of

the summer until autumn. My notes are as follows : Mycelium thin, evanes-

cent: appendages about twelve, colored at base, sometimes septate, simple

or but little dichotomously forked; conceptacle black, 1-300 in., gregarious

on the upper side of leaves. Sporangium eight-spored. The spore-like forms

on the appendages have already been referred to. These were by no means
on all the plants, but occurred on this one as shown.

Microapliseria, extensa, G. & P., (Plate IV, Fig. 2.) On Quercus rubra
and Q. palustris in woods. The upper sides of the leaves are conspicuously

whitened.

M.friesii, Lev. Very common on Syringa vidgaris. The concepta-

cles are sometimes abundant, but not always. The divided and curled tips

of the appendages are very beautiful in perfect specimens.

M. ravenelii. Berk., (Plate IV, Figs. 7 to '11.^ On Gleditchia tri-

aranthns. This is certainly the same as my specimen in RaveneVs exxiccati,

but the mycelium is much more dense. In this respect it surpasses all I

have seen. The leaves are very white.

M. elevata, n. sp., (Plate II, Fig. 4.) Upper sides of leaves of Ca-
talpa, bigmonioides. Mycelium thin, web-like, rather evanescent. Concepta-
cles 1-250 in., conspicuously reticulated, raised from the leaf ; appendages
about twelve, colored at base, often simple, sometimes branched near the

base, usually 2 to 4 times dichotomously forked, very long ; sporangia four.

17. Sachs' Text Book of Botany, English Ed., 1875, p. 256.



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oYal, strongly rostrate. This appears to be so distinct from any description 
given that l have named it as new. .Xot uncommon. 

E1:1Jsi'plu·, --- (Plate 11�, Fig. 1.) On Aster p1miceus. One con­
ceptacle alone found. 

E. lamprocarpa, Lr>v. On Phlox (Old :Maid's Pink.)
E. nwrtii, LI..·. Very common on leaves and stems of peas. The

cultivation .of garden peas in late summer and autumn is precluded from 
the effects of this fungus as much as from the weevil which infests them. 

Erotimn herbariorum, LI.·. On plants in cabinet. Common every­
where. 

These are all that were found in these two families, except one of th� 
latter on leaves of Liriodmdron tulip ifera, whi h was not matured enough 
to determine. Botryopiwn p11lchrum should not have been given among 
the parasitic plants, as it is only found on decaying herbage. The figure is 
more slender and the branches longer than Cooke's figure. The species may 
not be correct. Fear of occupying too much space causes the omission of 
further notes. 
























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