R E I N W A R D T I A

Published by Herbarium Bogoriense, Bogor. Indonesia
Vol. 8, Part 2, pp. 333 — 334 (1972)

NOTE ON HYMENODICTYON (RUB.) AND ITS OCCURRENCE IN
MALESIA, ESPECIALLY IN WEST JAVA

C. G. G. J. VAN STEENIS

Rijksherbarium, Leyden, Netherlands

The genus Hymenodictyon is a genus of often large, often deciduous
trees which is widely distributed over the African and Asian-Malesian
tropics, with 11 species recorded for Madagascar. Within Malesia it is
found in most major islands cq. island groups, but from Borneo and
New Guinea there are no collections yet known to me. From the Malay
Peninsula it was recorded only once, viz. from the Langkawi Is. in the
extreme northwest on the border with Thailand. Over the whole range
records are very patchy and scarce.

The above given distribution would suggest a slight preference for
a seasonal climate. This is also stated by Backer & Bakh. f. (Fl. Java 2:297)
who say that it occurs in Java only in the eastern half, "especially in
periodically dry areas, rare".

In scanning the collections at Leyden, it appears, however, that the
climatic response is certainly not valid for the whole of Malesia, as
specimens of the island Morotai (N. Moluccas), South Sumatra (Palembang
Res.), and West Java are certainly from everwet rain-forest. It is probably
more the rarity of Hymenodictyon than the climate which encouraged
this suggestion. I get the impression that it is rather indifferent to
climate, but that its rarity is probably caused by its reproduction and
ecology which approach that of a nomad plant, which can only settle
temporarily in dense rainforest and needs open space and spots for its
germination and upgrowth seedlings and saplings. This would also explain
why it is more frequently found in dry areas, because these offer more
open spaces that the dense rain-forest.

The data from the invaluable work of Troup on the, Silviculture of
Indian Trees (vol. 2: 625 seq.) support this opinion. He says that:
— "H. excelsum Wall, occurs scattered throughout the dry, mixed
deciduous forests of India and Burma, being particularly common on
loose dry deposits of boulders and debris along the base of the outer hills

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334 R E I N W A R D T I A [VOI,. 8

in the sub Himalayan tract, especially where the subsoil level is at great
depth". The associates he mentions are characteristic for seasonal climatic
conditions. "It is also frequently met with on sandy or stony soils on
alluvial ground near rivers, and in savannah lands. Bare ground is
favourable to germination and subsequent survival, young seedlings being
killed off in quantity where weeds are present; shade also contributes
towards failure of natural reproduction which explains to some extent
its comparative scarcity in many localities". This is, therefore, well in
agreement with the occurrence in Malesia and points to nomad ecology.

However, Troup does not mention its occurrence in rain-forest
localities, which is in Malesia certain for Morotai and Palembang, and
with two indubitably native localities in the everwet forest of West Java,
viz. an old collection from Mt. Gedeh — because of its sterile state hitherto
filed under Rubiaceae inc. sedis — and a new collection from the extreme
part of SW. Java, viz. Peutjang I. off Udjong Kulon Peninsula.

The locality on Mt. Gedeh, one. of the most intensively explored areas
in Java, sustains also its rare and possibly ephemeral occurrence, as it
has never been collected again there in a century. The records are:

WEST JAVA, Mt. Gedeh: Hoidsoortcn van den Gedeh, No. 567, sterile, vern. (prpbably
Sundanese) ki-gala. This collection was according to me (Fl. Mai. 1: 248. 268) made
at the instigation of Junghuhn, probably end 1850s. Udjong Kulon Peninsula:
Peutjang I., at sealevel, fl. J. 1964, N. Wiraivam 408.

As to the precise species identity there is uncertainty, three species
having been recorded from Malesia, viz. H. excelsum Wall., H. horsfieldii
R. Br. from Java and H. koordersii K. Sch. from Celebes. Backer &
Bakhuizen van den Brink Jr. maintain the view of Valeton that the first
two are different species. It may well turn out that we have only one
species, but this needs further detailed research.

It is a pleasure to contribute to this Reinwardtia instalment dedicated
to Dr. A. J. G. H. Kostermans who, assisted by young colleagues, stimulated
so much the botanical exploration of Udjong Kulon and adjacent isles and
discovered or re-collected not a few most interesting woody plants in this
part of West Java which was, since Kuhl & Van Hasselt's exploration one
and a half century ago, botanically badly neglected.


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