10 NATURE AND RELATIONS OF BIO-ECOLOGY 



mal assemblages. This relation once established, certain problems 

 in animal ecology would be much simplified, for whereas the animal 

 assemblage is at first obscure, that of the plants is evident, its char- 

 acteristic physiognomy serving as an index to the animals of the com- 

 munity. It was concluded that the evidence drawn from the study 

 of the sand prairie, though very incomplete, was in accord with the 

 theory and justified the treatment of the plant and animal associations 

 together. 



This theme was further developed in an analysis of the internal 

 relations of terrestrial associations (1914), as a result of which it was 

 concluded that plants and animals agree in similar response to the 

 common environment and in types of geographic distribution. _ It 

 begins to appear that plant and animal assemblages are coextensive 

 parts of a biotic association, which as a whole constitutes the real 

 terrestrial community of living organisms. Plant and animal assem- 

 blages are mutually interdependent, but the plants are dominant in 

 established associations. Such assemblages are composed of ecologi- 

 cally similar groups correlated with the same physical factors or with 

 each other. 



Gams (1918). Gams considers that no logical ground exists for ex- 

 cluding animals from communities of organisms, and hence he incor- 

 l^orates these in the vegetation. To him, "vegetation research" is 

 synonymous with his new term "biocenology" and with "biocenotics" 

 of the zoo-ecologists, both of which he regards as closely related to 

 ecology, though not identical with it. His discussion, however, is 

 confined largely to plants, the most important exception being his 

 outline of the life forms of the combined plant and animal kingdoms. 

 This is based upon the assumption that the criteria available take 

 rank in the following order: (1) motility, (2) substratum, (3) habitat, 

 (4) nutrition. This is thought to be supported by the general accep- 

 tance of plankton as a biotic community. The three major divisions 

 of his system are as follows: (1) adnate or attached form, EpJiaptome- 

 non; (2) radicate or rooted form, Rhizumenon; (3) errant or free 

 form, Plan omen on. The first group is divided into aquatic, amphibi- 

 ous, aerial, and innate, further subdivisions being autotroph and 

 heterotroph, saprobe, parasitic, and phagont. 



Gams emphasizes the fact that, while biocenose has been employed 

 by a number of zoo-ecologists, viz., Dahl (1903), Enderlein (1908), 

 Babler (1910), Shelford (1911), Hesse (1912), Doflein_ (1914) , and 

 Thienemann (1918), this has been in connection with animal commu- 

 nities of very unequal rank. He further suggests that phytocenose 

 may be utilized for the plant population of a habitat and zoocenose 

 for the animals, but this suggestion is scarcely in harmony with the 

 concept of the biotic community. 



