PLANT ASSOCIATIONS 289 



foliage. The density of growth is always remarkable, re- 

 sulting in a gigantic jungle, with plants at every level, inter- 

 laced by great vines and covered by perching plants ; in 

 fact, all the space between the ground and the tree-tops seems 

 to be packed with plants. 



155. Summary. Different areas support different kinds 

 of plants, and plants naturally assembled on any area form 

 a natural association. Each association of plants has its 

 own habitat. The chief features of a habitat that determine 

 what plants shall occupy it are available water, temperature, 

 soil, exposure to light, prevailing winds, etc. 



Certain kinds of plants dominate and give character to 

 the association established upon a habitat. The other mem- 

 bers of the association must adjust themselves to the domi- 

 nant plants, and learn to live under whatever conditions 

 the dominant plants permit. In any association of plants 

 the plant population is in proportion to the number of 

 kinds of plants included in the association. A single kind 

 of plant cannot produce as many individuals on a given 

 area as can several kinds of plants. 



The most important fact about plant associations is their 

 succession, which means that an association makes a habitat 

 unfit for itself and more fit for some other association. The 

 succession on any area ends in a climax association for that 

 region, and in general the climax is some kind of forest 

 association. 



