304 ZONES AND REGIONS [Pt. Ill, Sect. I 



work, and know it only from the abstract given by Drude \ Of the 

 luxuriance of the rain-forest in Samoa a vivid representation is given in 

 Fig. 130. 



3. OECOLOGICAL CHARACTERISTICS OF PLANTS 

 GROWING IN THE RAIN-FOREST. 



The plants of the evergreen tropical rain-forest are markedly hygro- 

 philous, and, with the exception of some epiphytes which are exposed to 

 quite peculiar conditions of existence, they possess a corresponding 

 structure. All the features that in an earlier chapter we recognized as 

 characteristic of the vegetation in a very moist climate, such as feeble 

 formation of cork and of fibres in the axial parts, ombrophilous foliage, 

 hydathodes, dripping-points to the leaves, are strongly marked in them. 

 The last-mentioned peculiarities of hygrophilous plants appear to be more 

 strongly developed in the tropics than in the temperate zones, and, for the 

 most part, have been first observed there. 



In the following paragraphs a description will be given of some of these 

 peculiarities of the tropical rain-forest, which without being entirely absent 

 from other zones yet in the tropics alone attain great importance and 

 determine the oecological features of the vegetation. 



i. TREES AND SHRUBS OE THE RAIN-FOREST, 



The stems of the trees whose crowns form the leaf-canopy that is usually 

 invisible from below are of very unequal thickness, and usually thinner than 

 in less dense and humid virgin forests. Many of them are supported at 

 their base by buttresses, which sometimes consist of cylindrical roots spring- 

 ing from the stem at some distance from the ground, as in species of 

 Cecropia and Myristica ; but much more frequently these buttresses assume 

 the form of plank-like outgroivths of the base of the trunk and of the upper- 

 most roots, and they may be termed plank-buttresses (Fig. 143). These 

 plank-buttresses, radiating from the base of many tree-trunks, reach up to 

 a height mostly of one or two meters above the ground, and thus form 

 deep niches, in which there is not infrequently ample space for two or 

 three men. The thickness of the planks is often so small that they can 

 be employed as tables without any further manipulation. Such buttresses 

 are by no means common to all the trees of the rain-forest, but to the 

 minority only ; they chiefly occur on very tall stems that are comparatively 

 thin above, but also on the massive stems of fig-trees. 



As in the case of so many other phenomena of tropical vegetation, the botanic 

 garden at Buitenzorg affords a splendid opportunity for studying plank-buttresses 

 of different shapes, and indeed, as is not usually the case in the forest, on trees 



' Drude, Pflanzengeographie, p. 495. 



