54 2 RELATION TO ENVIRONMENT. 



sun woods occur in those regions of considerable rainfall, but 

 with a dry period, during the latter part of which the trees are 

 bare of leaves. The woods, therefore, are markedly of a tropo- 

 phile character, resembling in this respect the deciduous trees 

 which lose their leaves during the winter period. The trees are 

 less in height than those of the evergreen forest, are rich in woody 

 lianas and in herbaceous epiphytes, but poor in woody epiphytes. 

 3d. The savanna woods and the thorn woods. These are rarely 

 evergreen during the dry period. The savanna woods are about 

 20 meters high, are poor in undershrubs, lianas, and epiphytes, 

 but rich in grasses and other herbs growing on the ground. The 

 thorn woods as well as the savanna woods are xerophile in char- 

 acter, very rich in undershrubs and slender-stemmed lianas, are 

 poor in herbs and grasses, and mostly without epiphytes. 



1025. The evergreen tropical forests. These are remarkable 

 for the great number of species and of individuals, and for the 

 great mass of vegetation. There is usually such a dense growth of 

 tall forest trees that the light is shut out from the forest floor and 

 interior to such an extent as to largely prevent the growth of 

 smaller vegetation upon the forest floor. The forest is therefore 

 noted for its epiphytes, herbaceous as well as woody, which grow 

 in great numbers upon the branches, within or just beneath 

 the forest canopy, where they are better situated in reference 

 to light. It is interesting to note that in the reforestation of 

 the volcanic areas in west Java, for example, a number of these 

 epiphytes are found growing on the bare lava, among ferns and 

 other low vegetation. Here they have a suitable relation to 

 light, but when the forest finally develops in such regions, as it 

 will if undisturbed, these epiphyte species now growing on the 

 ground will migrate to the forest canopy. The evergreen broad - 

 leaved forests are largely within the tropics, though there is some 

 extension into parts of the south temperate region. While the 

 forest represents the climax type of vegetation, the evergreen 

 forest of the tropics is the climax type of forest formation. The 

 evergreen tropical forests are found in those tropical areas where 

 the rainfall is very great and is also evenly distributed throughout 



