No. 571] 



415 



ciation is built Up largely from a knowledge of the ecol- 

 ogy of all the organisms which compose it. 



A. Ecological Constitution of the Organism 

 The constitution of the organism is the sum-total of 

 those of its characters which enter into relation with 

 environment. These are commonly classified as structural 

 and physiological. For the purposes of this discussion 

 it would seem preferable to subdivide physiological char- 

 acters, restricting the term physiological to denote those 

 characters concerned with ordinary metabolic processes 

 of the organism, and excluding those having to do with 

 life-history and rates of reproduction (these may be dis- 

 tinguished as biographical and numerical 1 ) and also, when 

 dealing with animals, those related to behavior (psycho- 

 logical characters). The constitution of the organism in 

 relation to environment will be discussed in terms of 

 these classes of characters. 



B. Constitution of the Plant in Relation to 



The environmental influences in the association are of 

 three kinds: (1) physical, (2) plant, (3) animal. Each 

 plant and each animal must obtain from each of these 

 three constituents of its environment certain necessaries; 

 it has certain structural and physiological characters 

 which enable it to obtain these necessaries, and to with- 

 stand adverse environmental influences. 



ent from those of animals. A tabular comparison of 

 these relations has been made by Shelf ord (A: 593). As 



