388 BOTANICAL GAZETTE [November 



growth in which Agropyron and Boutelona occur together is 

 frequently seen. In the pure wheat-grass, Astragalus goniatus 

 Nutt. and Artemisia gnaphalodes Nutt. together form one very 

 definite society, while Tium Drummondii (Dougl.) Rydb. {Astraga- 

 lus Drummondii Dougl.) characterizes a second. A third (fig. 4) 

 is marked by Artemisia aromatica A. Nels. Carex stenophylla 

 Wahlenb. and C. pennsylvanica Lam. dominate very small areas, 



ally within the ^ 

 The wheat-grass 



in 



tending 



ward along the foothills. These interrupted growths would prob- 



much 



grama 



THE BUNCH-GRASS ASSOCIATION 



Bunch-grass association. — Shantz i8 f p. 54. Eastern Colorado. 

 High prairie. — Hall 6, pp. 30-35, in part. Eastern Kansas. 

 Andropogon-Sorghastrum growth. — Hitchcock 9, p. 64. Eastern Kansas. 

 Bunch-grass formation. — Pound and Clements 13, p. 354. Nebraska. 

 Grasslands of the semi-humid black-soil prairies. — Bray i, p. 86, in part. 



Texas. 



A ndropogan 



—Harvey 8, pp. 287, 288. South 



Dakota. 



Bunch-grass association. — Gleason 5, p. 47, in part. Illinois. 



Dry prairies of the prairie-grass formation. — Harshberger 7, p. 523 (after 

 Beendel 2, p. 34). Central Illinois. 



Bunch-grass formation. — Harshberger 7, 532 (after Pound and Clem- 

 ents) . Nebraska. 



The bunch-grass association, though occupying a very small 

 part of the area studied, appears to be similar in composition to 

 bunch-grass growths over the extent of the prairie province. It is 

 best seen near the outer ends of the tops of the higher mesas south 

 of Boulder (mixed bunch-grass consocies). The soil is gravelly, the 

 growth somewhat open, about 35 per cent of bare surface being 

 exposed. A number of species dominate together, in about the 

 following order of importance: Andropogon scoparius Michx., 

 Koeleria cristata (L.) Pers., Andropogon fur catus MuhL, Sorghastrum 



nutans (L.) Nash, Muhlenbergia gracilis Trin., Atheropogon curli- 



