272 NOTES AND COMMENT 



brought about a closer relation of plant occurrence to the physical fac- 

 tors. These stable communities have been little studied, and chiefly 

 because they require attack from a very distinct point of view. The 

 theory of successional plant ecolog}^ has now been thoroughly elabo- 

 rated, even if the work which it suggests has not been finished. The 

 study of the relatively stable communities resolves itself into an inves- 

 tigation of the relation of plant distribution and plant activities to cli- 

 matic factors. The abeyance of successional phenomena and the 

 immanence of physiological problems combine to make the investigating 

 of stable communities take a different course from that which has com- 

 monly been pursued in ecological field work. To state that the corre- 

 lation of plant ranges with climatic factors is based on assumption is 

 merely to emphasize the need for work on stabilized vegetations from 

 a physiological point of view. 



