THE STRUCTURE OF CLIMAXES 241 



unlikely that quantitative studies on a larger and more extensive scale 

 may also render it desirable to distinguish societies of subdominants, 

 especially in the benthos. 



Kinds of Influents. As indicated previously, the term influent is 

 practicall}' to be restricted to animals because of their role as co- 

 actors. In water climaxes, the effects of animal dominants have not 

 been evaluated as to the relative importance of reaction and coac- 

 tion. Influents fall less definitely into the primary categories of 

 dominants, namely, land and water on the one hand, and climax and 

 serai on the other. They may in time be gi'ouped in accordance with 

 importance of coaction into various categories, such as major influ- 

 ent, minor influent, subinfluent, and veinfluent. Lack of knowledge 

 and opportunity for the study of the more important influences due to 

 extirpation and reduction in numbers, and fluctuation in abundance, 

 renders such classification difficult in some communities at present. 

 Major influents include the larger mammals and birds or intermediate 

 forms of marked coactive significance, the fishes, and other aquatic 

 organisms of considerable size or vast number. Minor influents com- 

 prise the smaller rodents, insectivores, bats, most of the birds, am- 

 phibia and reptiles, and a host of marine forms. Subinfluents embrace 

 the larger insects, arachnids, snails, isopods, etc.; and veinfluents, the 

 disease organisms, micro-insects, the fauna of the soil, and the macro- 

 and microplankton. Though no hard-and-fast line can be drawn be- 

 tween these groups, especially in the present state of our knowledge, 

 they may serve to bring out the comparative roles of coactors in a 

 particular community. 



On the basis of abundance and time of appearance, smaller influ- 

 ents may be classified as prevalent or predominant when they are 

 present in numbers throughout the several significant seasons, as sea- 

 sonal when they occur during one or two aspects, such as spring, sum- 

 mer, etc., and as cyclics, when they exhibit marked fluctuations or 

 appear only at intervals, like certain cicadas. The larger influents 

 may fall into a similar grouping, though quite possibly their fluctua- 

 tions were less under primeval conditions. In many cases, migratory 

 species are influents in more than one climax and hence must be listed 

 as seasonals in two or more communities. Animals probably do not 

 range outside the biome in which they are influent farther than plants, 

 except when migratory; for example, a few grasses dominant in the 

 prairies may range east into New England in dry sandy spots, but 

 they bear no significant relation to the deciduous forest climax. The 

 difficulty on the animal side arises from lack of evaluation as to 

 abundance and lack of appreciation of the intricate interlacing of 



