386 BOTANICAL GAZETTE [November 



Grasslands of the high plains. — Bray i, p. 91. 



Grama-buffalo-grass association. — Shantz 18, p. 24. 



Grama-grass association, — Shantz 18, p. 21. 



Grama-grass formation. — Harshberger 7, p. 537 (after Pound and 



Clements). 



Buffalo-grass formation. — Harshberger 7, p. 528 (after Pound and 

 Clements) . 



The short-grass association in its typical form (Bouteloua- 

 Buchloe consocies) , as developed on the open plains, has been well 

 described by Shantz (18). The eastern half of the Boulder region 

 is covered principally by this growth. Near the mountains the 

 buffalo-grass (Buchloe dactyloides [Nutt.] Engelm.; Bulbilis dacty- 

 loides [Nutt.] Raf.) is very scantily represented, as also in the 

 northern part of the plains region. Its scarcity is made up by 

 increased abundance of the grama-grass (Bouteloua oligostachya 

 [Nutt.] Torr.), which dominates much of the area- It forms either 

 a pure or nearly pure growth (Bouteloua consocies), or, in the coarse 

 soil of the mesa-terrace, enters into a mixed growth (Bouteloua 

 mixed consocies). This growth is characterized by abundance of 



Euph 



elm.) Small, Psoralea tenuiji 



Lambertii (Pursh) Greene, and Grindelia squarrosa (Pursh) Dunal; 



(1) some few deeper-root 

 etc., typical in the more 

 plains region; and (3) ] 



tnd floristic elements 

 composites, legumes 



from 



Mertensia 



Geranium Parryi [Engelm.] Heller, etc.). Certain of these, as the 

 last two, are rarely found except at the base of surface rocks. Here 



from 



m 



shrub associations. 



mesa 



Shan 



the Bouteloua mixed consocies. A rather dry representation of this 

 growth is seen in the foreground of fig. 2. 



The different growths dominated principally by Bouteloua are 

 considered to be parts of the same association, rather than different 

 associations, for the resemblances aooear to be more constant and 



