e 
. 
: " 
422 
Shape of crown.—Aside from the regular oval or irregular tree crowns, 
a number of types worthy of mention were noted. Polysias nodosa, 
which in the parang usually has a single rosette of large compound leaves, 
in the closed forest reaches tree dimensions of considerable size and has 
from three to six short branches at the top, each of which ends in a 
rosette of leaves. Many Meliaceew have similar crowns; in young trees 
there is a single rosette, and in older ones there are rosettes on the ends 
of secondary and tertiary branches. This, as already shown, is the habit 
of Dracontomelum cumingianum. Koordersiodendron pinnatum has 
a similar habit. Orania palindan, Cycas circinalis, and a tree fern, 
Alsophila contaminans, are among the smaller trees which have a single 
rosette of compound leaves. Of those which have a single rosette of 
large simple leaves are Semecarpus gigantifolia, Macaranga mappa, 
and Ficus psudopalma. By far a majority of trees have an oval or 
spherical crown or a more or less irregular one. Aside from compound 
leaves of members of the Leguminose, the Meliacee, Burseracee, and 
Anacardiacee, most of the trees have simple, entire leaves. Those with 
a serrate or wavy margin are the exception. Guttered leaves are repre- 
sented, though sometimes obscurely so, by species in the Moracee (Ficus), 
Guttifere (Calophyllum and Garcinea), Myrtacee (Hugenia), and 
others. 
Bark of trees—Nearly all writers on tropical vegetation have called 
attention to the thin bark of tropical trees as compared with those grow- 
ing in temperate climates. This is due to the weak development of the . 
corky tissue. The measurement of the bark of 44 mature or nearly 
mature trees, representing different species, shows an average thickness 
of 6.87 millimeters. Of those measured, Palaquiwm luzoniense, with a 
bark 15 millimeters in thickness, represents the maximum, and Antidesma 
edule, with a bark 2 millimeters thick, the minimum. The cause of the 
weak development of the corky tissue is generally attributed to the effect 
of humidity on the formation of bark. Where the humidity differs, 
observations have not been extensive enough to show any appreciable 
variation between the development of bark on the same species in the 
trees of the Lamao Reserve, found in two or more plant formations. (See 
Pls. X, XI, XIX, XXI, XXII, XXIII, XXIV, and XXV, for bark 
‘characters. ) 
Notes collected in reference to the bark of nearly a hundred different 
species show that in a majority of cases this is smooth, and light gray or 
brown in color. In many instances the surface is more or less thickly set 
with corky pustules of various shapes and sizes. In the case of the rham- 
naceous Zizyphus zonulatus, short, thick pyramidal thorns are charac- 
teristic. In Diospyros pilosanthera the pustules are more or less thorn- | 
like, but do not assume any regular shape. In many trees with more or 
less smooth bark, it is shed at irregular intervals in large or small scroll- 
like patterns. In the myrtaceous T'ristania decorticata, as the specific 
