28 THE STUDY OF PLANT COMMUNITIES ' Chapter II 



some require a large continuous supply of moisture, others require 

 only a small amount which need be available only periodically. 

 Thus the climate of a region definitely controls the kinds of plants 

 that may grow there. The general vegetation type or growth 



FIG. 8. Spanish "moss" (Tillandsia usneoides), an epiphytic flowering 

 plant, growing on live oak, North Carolina coast— Photo by H. L. Blomquist. 



form, such as grassland, desert, or forest, is a product of the com- 

 plex of climatic factors effective in a region and can be used as a 

 generalized basis for evaluating the climate. For example, knowing 

 something of the growth forms able to survive under the extreme 

 conditions of moisture and temperature associated with a desert, a 

 repetition of these growth forms anywhere else in the world auto- 

 matically may be accepted as indicative of desert conditions. The 

 scrubby broad-leaved evergreens (chaparral) that cover much of 

 southern California are a product of the climatic conditions pe- 



