424 The Philippine Journal of Science ww 



places are rare, as both the understories and ground covering are 

 usually very dense, the average undergrowth in a good forest 

 being always much more abundant than in a well-developed 

 deciduous forest of the temperate zone. The forest is, however, 

 far from being an impenetrable jungle. One can pass through 

 it readily if he carries a long knife to cut the spiny leaves of the 

 rattan, while even this is unnecessary in the best types. How- 

 ever, the edges of even the best types of forest are very dense 

 (Plate IV, fig. 1). 



Comparing the appearance of the dipterocarp forest with a 

 deciduous forest of the temperate zones, the chief difference 

 lies in the greater density of the dipterocarp type. This dif- 

 ference in density includes foliage, undergrowth, and the num- 

 ber of trees and vines. Next to density comes the presence 

 of palms, particularly of the rattans, which form such a con- 

 spicuous element in the undergrowth. Besides this, the pecu- 

 liarities of certain trees should be noted. These are buttresses, 

 cauliflory, and the presence of strangling figs. A considerable 

 proportion of the tall trees have tremendous planklike buttresses 

 (Plate VI, fig. 1), which in extreme cases extend several meters 

 from the tree and probably help to support it. The strangling 

 figs, species of Ficus, present a most peculiar appearance (Plate 

 III, fig. 1). Starting as epiphytes in the tops of the trees, they 

 send down roots which become connected with the ground (Plate 

 III). Branches from these roots grow around the tree and coa- 

 lesce either with each other or with a main root, until the trunk 

 of the tree on which the fig started, usually, becomes inclosed by 

 a network. As this grows it interferes with the growth of the 

 trunk, the fig leaves shade the tree, and roots of the fig interfere 

 with those of the tree. This combination usually results in the 

 death of the tree on which the fig is growing. The meshlike 

 support of the fig continues to grow until it may finally assume 

 the appearance of a solid trunk. These strangling figs frequent- 

 ly occur on the largest trees, but are much less numerous in the 

 best forests than in the poorer types. Cauliflory occurs in a 

 number of species, particularly of the genus Ficus. However, 

 neither strangling figs nor cauliflorous trees are present in the 

 best types in sufficient numbers to influence the general appear- 

 ance of the vegetation. 



If we were to sum up the impression which one gets in pass- 

 ing through a dipterocarp forest it would be something like 

 this: A tall, dense forest is seen in which large trees and small 

 ones are crowded together until their leaves very fully occupy all 

 of the available space, while the ground is covered with a 



