384 BOTANICAL GAZETTE [November 



Growth dominated by usually deep-rooted grasses; more extensively 



developed in the less arid central and eastern parts of the province, or 



Prairie region, and of local distribution along the mountain-front. 



Dominant plants of tuft growth-form (of the Andropogon type) ; many of 



the secondary species pronounced xerophytes; growth most extensively 



developed in the central part of the prairie region. 



Bunch-Grass Association 

 Dominant plants close-growing mesophytic grasses, usually sod-formers 

 (of the nature of Poa pratensis) ; secondary species composed of a larger 

 proportion of mesophytes; most extensively developed in the eastern part 



of the prairie region, particularly along the forest border. 



Prairie-Grass A ssociation 



Associations of local, though commonly wide, distribution within the area of 



the province; either established or primitive stages of vegetation; frequently 



not restricted to the area of the province (Minor Associations). 



Associations typical of habitats representing extreme conditions within the 



area of the province, in which local physical conditions, not being in accord 



with climatic conditions, determine the character of the vegetation to a 



large extent. The growth is thus as stable and permanent as the physical 



environment (Local or Edaphic Associations) . 



Associations of rock or of non-alkaline soils. 

 Growth of rock surfaces; well developed < 



Associations of dry soil. 



Lichen Association 

 and exposed mesa- 



crests. 



In the most extremely xerophytic and stony habitats; dominant 



plants cespitose, prostrate. 



Mat 



In less extreme habitats of coarse or loose soil; dominant plants 



- 



xerophytic grasses. 



Stipa-Aristida Association 



In sandy soil; not well represented within the area studied. 



Sand-Hills Mixed 



Associations 



In moist soils, usually bordering depressions. 



Hordeum jubatum Association 

 In wet or submerged soils. 



saline or alkaline 



Associations 



In deep dry alkaline soil, frequently sandy; growth dominated by tall 



xerophytic shrubs. M , m . 



Chrysothamnus-Sarcobatus Association 



* Swamp associations, dominated by species of Typha, Scirpus, Calamagrostis , 

 Spartina, etc., are about the same within the region studied as in other parts of th6 

 United States, and are not here discussed. 



