THE PLANT FORMATION 



225 



of each. Arrange them in the order of abundance as indicated in sec- 

 tion 219, and decide which are facies and which principal or secondary 

 species. 



If the quadrat is listed in the early spring, then marked and listed 

 late in May or early in June, the prevernal and vernal aspects may be 

 compared. When it is possible, it should be listed again at the end 

 of July, and finally in September for the summer and autumn aspects. 



239. The parts of a formation : the consocies. The hetero- 

 geneity of a formation is due to parts of varying rank which are 



Fig. 85. An area controlled by the rye grass, i.e., an Elymus consocies, 

 in the Elyvius-Muhlenbergia formation. 



called forth by historical as well as by physical factors. These 

 parts or divisions, in the order of rank, are the consocies, the society, 

 the community, and the jamily. In formations controllo<l by two 

 or more facies, the latter are very rarely if ever unifoi-nily dis- 

 tributed. One will be more dominant here, another there, and 

 a third elsewhere, or certain ones may be groupetl together in 

 one place, and others in another. The various areas that arc 

 controlled in this way ])y the facies are termed consocies. In 

 the grass formation of the prairies there are several facies, \\a., 



