ESSENTIAL NATURE OF SUCCESSION. 7 



Functional aspect. — The motive force in succession, i. e., in the development 

 of the formation as an organism, is to be found in the responses or functions 

 of the group of individuals, just as the power of growth in the individual lies 

 in the responses or functions of various organs. In both individual and com- 

 munity the clue to development is fimction, as the record of development is 

 structure. Thus, succession is preeminently a process the progress of which 

 is expressed in certain initial and intermediate structures or stages, but is 

 finally recorded in the structure of the climax formation. The process is 

 complex and often obscure, and its component functions yield only to persist- 

 ent investigation and experiment. In consequence, the student of succession 

 must recognize clearly that developmental stages, like the climax, are only a 

 record of what has already happened. Each stage is, temporarily at least, a 

 stable structure, and the actual processes can be revealed only by following 

 the development of one stage into the succeeding one. In short, succession 

 can be studied properly only by tracing the rise and fall of each stage, and not 

 by a floristic picture of the population at the crest of each invasion. 



