IX, A, 5 



Brown and Mathews: Dipterocarp Forests 423 



attain a length of more than 100 meters. Rattans in the rosette 

 stage usually form the most conspicuous part of the ground 

 covering, and difficulty in penetrating the undergrowth is usually 

 due to the spines of the rattan rather than to the density of 

 the vegetation. 



The composition of the ground covering other than the rattans 

 varies greatly in different situations. On ridges of the lower 

 slopes of mountains in regions with a pronounced dry season it 

 consists almost altogether of small woody shrubs. In ravines, 

 near streams, ferns are numerous, while miscellaneous her- 

 baceous plants occur in considerable numbers. Near the upper 

 edge of the dipterocarp forest and in regions without a pro- 

 nounced dry season, ferns and herbaceous plants are often 

 present in large numbers even on the ridges. 



Large vines are a characteristic feature of the dipterocarp 

 forest (Plate I, fig. 1), and in poorer-developed types of forests 

 they may be prominent enough to influence the appearance of 

 the vegetation markedly, while in the best types they are much 

 less noticeable. In the poorer and particularly in cut-over types 

 climbing bamboo is frequently well developed. The greater de- 

 velopment of vines in the poorer types is connected with the fact 

 that more light comes through the canopy of the top story than 

 in the best types. 



Epiphytes, which are very prominent in the mossy forest, are 

 in the dipterocarp type chiefly restricted to the larger branches 

 of the tall trees where they form regular aerial gardens. The 

 chief constituents of these are ferns — particularly humus-gather- 

 ing ones, such as species of Drynaria — xerophytic orchids, and 

 species of Hoya. These are frequently so completely hidden by 

 the foliage beneath them as to be invisible from the ground. 

 Epiphytes on the trunks of the trees are rather scarce and, with 

 the exception of the bird's-nest fern (Asplenium nidiis), are 

 usually inconspicuous. The bird's-nest fern, on the other hand, 

 with its fronds a meter or more in length is the most striking 

 epiphyte in the forest. It does best in somewhat moist local- 

 ities, and is almost entirely absent from dry ridges. 



We have seen that the dominant trees of the forest are dip- 

 terocarps and that as these increase in number and size the 

 other constituents of the forest become less prominent. This is 

 probably connected with the fact that as the dipterocarps become 

 better developed they shut out more light from the lower stories. 

 In the best forests there are sometimes small patches where the 

 dipterocarps cast such a dense shade that there is practically 

 nothing growing on the ground under them. However, such 



