XEROPTTYTTC SOCIETIES 



509 



Fig. 459. — A deciduous forest, a mesophytic society consisting of Bass- 

 wood, Birches, Elms, Maples, and Oaks, under which grow many herbaceous 

 plants. After C. M. King. 



Xerophytic Societies. — These are the societies adapted to 

 drouj2:ht. Ainoiif!; xerophytic plants there are various adapta- 

 tions to drought, such as sunken stoniata, hairy epidermis, re- 

 duction of leaf surface, deep tap-roots, reservoirs within the 

 leaves or other parts of the plant for holding water, edgewise 

 position or rolling of leaves, bridging over the period of drought 

 in the form of seeds or subterranean structures, etc. 



Among the xerophytic societies are the rock societies, composed 

 chiefly of Lichens {Fig. JfiO) and Mosses which grow on dry jind 

 exposed rocks; desert and dry plain societies {Fig. 461) where such 

 plants as Cacti, Sage Brush, Agaves, and Yuccas dominate; xero- 

 phytic thickets, composed of a dense mass of bushes and repre- 

 sented by the chaparral of the Southwest; and the xerophytic 

 forests, in which Pines, Spruces, and Firs, adapted to mountain 

 slopes and gravel ridges, occur. 



