THE INTERPRETATION AND APPLICATION OF CER- 

 TAIN TERMS AND CONCEPTS IN THE ECOLOGI- 

 CAL CLASSIFICATION OF PLANT COMMUNITIES^ 



GEORGE E. NICHOLS 



The Sheffield Scientific School of Yale University, New Haven, Connecticut 



During the past seven years much of the writer's study has 

 been along the line of local physiographic plant ecology, and the 

 need has constantly been felt of some logical and adequate, 

 yet at the same time simple and to a certain extent elastic 

 scheme which could be readily adapted to the ecological clas- 

 sification of the vegetation of any region. The groundwork 

 for such a classification is afforded by the principle of succes- 

 sion, the fundamental bearing of which on the relationship and 

 evolution of plant communities has been indisputably estab- 

 lished by the work of Cowles (7, 8, 9, 11), Wliitford (24), Clem- 

 ents (3, 4), Moss (16, 17) and others. The principal object 

 of the present paper is to outline a plan of classification which 

 it is thought will recommend itself because of its lack of com- 

 plexity and because of the readiness with which it can be ap- 

 plied, and in this connection to express the writer's views re- 

 garding the interpretation and application of certain ecological 

 terms and concepts. Incidentally, several new terms, or rather 

 combinations of terms already in use, are introduced, which it 

 is thought will prove serviceable by verj^ reason of their sim- 

 plicity of interpretation and application. The scheme of clas- 

 sification itself is by no means wholly new or original. It is 

 the outgrowth, and perhaps not a very radical modification, 

 of the classification originally devised by Cowles (S). 



THE UNIT OF VEGETATION WITH REFERENCE TO HABITAT 



The association. From the standpoint of physiographic ecol- 

 ogy (synecology) the association, in the last analysis, repre- 



' Contribution from the Osborn Botanical Laboratory. 



305 



THE PLANT WORLD, VOL. 20, NO. 10 

 OCTOBER, 1917 



