Te eg eee ae ee ee ee Oe eT | 
419 
position for many individuals of Cymbidium aloifolium, Aerides quinque- 
vulnera, and Rhynchostylis violacea; on the higher and more xerophytic 
parts of the tree there were many specimens of the fern Drynaria querci- 
folia. The branches of Lagerstremia speciosa, Ficus caulocarpa, and other 
trees afford a good surface for the germination of orchid seeds; the semi- 
parasitic Hoya multiflora is also not infrequently encountered. Several 
species of orchids, and the ferns Drynaria, Vittaria lineata, were noted 
on the branches of the tall Dipterocarpacee. Species of Loranthacec, 
although present, are less common than they are in the parang. 
Herbaceous vegetation—One of the surprises of the forest is the 
scarcity of herbaceous plants growing in the dense shade during both 
the dry and wet seasons. Even in the open places there are found 
only a few geophilous Aracee, some grasses, small species of Acanthacee - 
as Gymnostachyum affine, Hypoestis subcapitatus, Lepidagathus hyalina, 
and others. Scattered throughout the forest is the sedge Hypolytrum 
compactum. ‘This species, with a few ferns and Begonia rhombicarpa 
on the more damp slopes, are the only truly herbaceous plants which were 
noted in the dense forest. 
Plank buttresses—Schimper ** has called attention to the prevalence 
in tropical countries of trees with plank buttresses or board roots. He 
claims that these are a peculiarity in a tropical climate where the rainfall 
is abundant and that they are found in the evergreen-rain, and in most 
of the deciduous, monsoon forests. 
Prevalence of buttresses—In the Anisoptera-Strombosia formation 
out of 39 fairly mature trees 15, or 38 per cent, had no buttresses, 13, 
or 33 per cent, had buttresses over 0.5 meter, and 11, or 29 per cent, less 
than 0.5 meter in height. The buttresses assume various shapes. Some 
extend up the trees to a height of 3 meters or more and are less than a 
meter in width; others are as broad as they are long; still others, usually 
low ones, branch. Of those observed, species of Anacardacew (Drancon- 
tomelum cumingianum and D. mangiferum) exhibit the best-developed 
ones, the buttresses of one specimen of D. cumingianum being 34 meters 
in height by 3 in width. As a rule, young trees show but little or none 
of this development. Old trees of Dipterocarpus vernicifluus may or 
may not have them. One of these showed a buttress which was narrow but 
at least 7 meters in height ; another equally large tree had none. Hugenia 
glaucicalyx has three equally strong buttresses which are developed in 
such a way as to divide the circumference of the trunk into three nearly 
equal parts. (See Pls. X, XI, XII, XXI, XXII, XXIII.) 
Cause of buttresses.—The buttresses seem to be correlated with broadly 
developed crowns (Pl. XII). Dracontomelum cumingianum, for in- 
stance, a tree usually growing in open places, has long, scraggy branches 
with coarse twigs on the ends of which are rosettes of large, compound 
leaves. In the forest where the crowns are dominant, and where they 
7 Loe. cit., 304, 305. 
