1914] VESTAL— PRAIRIE VEGETATION 383 



front, and often definitely to be correlated with particular environ- 



men 



Synopsis of the associations 



The following associations, with the exception of several of the 



hin, and usually restricted to, the 



local growths, are typical wi 



North America 



terized by low winter rainfall and grassland vegetation (Prairie 

 Province, Pound and Clements 12; Gleason 5, p. 43). Prac- 

 tically all the associations are considerably variable in composition 

 over their range, which in most cases is extended. No single cri- 

 terion has been depended upon in classifying the associations. 2 



Associations of extended and general distribution within the area of the prov- 

 ince; established vegetation, relatively stable or permanent, occupying the 

 more extensive habitats provided by climate and physiography (Climatic or 

 Major Prairie Associations) . 



Growth dominated by surface-rooted grasses, extensive in the more arid 

 western part of the province, or Great Plains region. 



Dominant plants of low mat form (the short-grass growth-form of grama- 

 grass and buffalo-grass). 



Short-Grass Association 

 Dominant plants taller (wheat-grass); growth extensive in northern parts 

 of the plains region, and extending southward locally along the mountain 



front. 



\V heat-Grass Association 



viduals. It seems advisable at present to make our concept of the plant association 

 quite broad, and to recognize that there are different types of associations. 



A consocies, as here used, refers to an appearance or representation of an associa- 

 tion characterized by one or several of its dominant species. English ecologists use 

 facies in the sense that consocies is here used. A society of an association is taken to 

 mean a representation of an association distinguished by abundance of one or several 

 secondary species, using the word secondary to include "principal" and "secondary" 

 species. Certain ecologists would use society in the sense that consocies is here used, 

 preferring to use consocies as synonymous with association, reserving the latter term 

 for referring generically to plant growths in general. The writer prefers to distinguish 

 between growths characterized by dominant species and those named for secondary 

 species, by calling the first a consocies, the second a society. It is apparent that there 

 are a number of different kinds of societies. The present use of consocies is that of 

 Gleason (5), who gives criteria (p. 38) for determining whether two growths represent 

 distinct associations or two consocies of the same association. 



a The associations within a particular region form a complex, which may be 

 classified in different ways, according to the purpose of the study. Bases of classifi- 

 cation have been discussed by the writer (Local distribution of grasshoppers in rela- 

 tion to plant associations. Biol. Bull. 25:150. 1913)- 



