THE STRUCTURE OF CLIMAXES 239 



such significant reactions upon the habitat, or in water upon the other 

 community constituents, as to control the community and assign to the 

 other species subordinate positions of varying rank. The resulting 

 interrelations have been analyzed in considerable detail for land-plant 

 communities (Clements, Weaver, and Hanson, 1929), but it is quite 

 probable that the zoophytes of coral areas exhibit them in a degree 

 not unlike that of grasses and shrubs. The graded series from these to 

 the motile dominants of marine pelagic and fresh-water biomes pre- 

 sents such relations in constantly diminishing measure, but when more 

 is known of the response, reaction, and coaction of the animals con- 

 cerned, it is probable that pronounced dominants will be found 

 throughout. 



The major characteristics of dominants may be indicated as fol- 

 lows : 



1. Dominants receive the full impact of the climate or of the aerial 

 factors in the case of terrestrial seres. 



2. They are the species best adjusted to climate or habitat as the 

 case may be, and hence are regularly most abundant in terms of 

 density or weight, as well as most stable in reproduction. 



3. They react directly upon the climate, modifying water and light 

 relations especially on land, and the gas and salt content in the sea. 



4. Climax dominants take possession of territory and hold it 

 against all comers as long as the climate oscillates only within its 

 proper range, while the occupation of serai dominants is limited by 

 the succeeding stages. 



5. Climax dominants are able to continue to grow and reproduce in 

 the conditions due to their reactions, while serai ones react upon the 

 habitat in such a way as gradually to favor the invasion of their suc- 

 cessors. 



6. Dominants on land, by virtue of life form and abundance in 

 particular, are the major sources of food, material for building, and 

 shelter, and usually constitute the basis for the ruling coactions, which 

 serve as a primary bond in the biotic community. 



7. Codominants are essentially dominants in terms of reaction or 

 coaction and control, but differ from the typical dominants of the 

 community in the nature of these processes, since they are consti- 

 tuted by plants in communities chiefly dominated by animals, or the 

 reverse. 



Subdominants. A subdominant has been defined as a species that 

 exhibits a secondary dominance within the area controlled by a 

 dominant. It gives character to pure or mixed societies, either spatial 



