452 A TEXTBOOK OF GENERAL BOTANY 
different from tropical rain forests, in that the trees have thick 
bark and annual rings of growth in the wood and lack but- 
tressed roots. 
Xerophilous forests. Dry tropical and subtropical regions which 
are not dry enough to produce deserts support either xerophilous 
forests (Figs. 241, 504) or grassland. The xerophilous forests 
may be either evergreen or deciduous. The trees are usually of 

Fria. 507. Growth of mosses and a filmy fern on a trunk in elfin mossy 
forest near summit of Mount Maquiling, Philippine Islands 
low stature as compared with rain or monsoon forests, but there 
are exceptions, the giant Hucalyptus forests of western Australia 
being pronounced xerophilous forests. The vegetation 1s more 
open than in rain forests or monsoon forests, and the leaves are 
much more xerophytic than in the latter types. The xerophilous 
forests often grade into bush land (Fig. 509), grassland, or desert. 
Grassland. Grassland in tropical and subtropical regions usu- 
ally takes the form of savanna, in which widely spaced trees occur 
with the grass (Fig. 510). In temperate regions grasslands are 
