236 MISC. PUBLICATION 200, U. S. DEPT. OF AGRICULTURE 



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Figure 312. — Agropyron riparium, X 1. (Nelson 3965, Wyo.j 



Figure 313. — Agropyron albicans, 

 3013, Wyo.) 



X 1. (Griffiths 



Illinois, Nebraska, Colorado, Nevada, 

 and Oregon. In the form growing on 

 the sandy shores of Lake Michigan 

 the lemmas are densely villous, but 

 villous forms occur in other parts of 

 the range of the species. 



This and the four following species 

 appear to intergrade, forming a poly- 

 morphous group. 



7. Agropyron elmeri Scribn. (Fig. 

 311.) Resembling A. dasystachyum; 

 culms on the average taller, more 

 robust, the spike longer (as much as 

 25 cm. long), the spikelets larger (as 

 much as 10-flowered and 2.5 cm. 

 long); glumes and lemmas usually 

 longer (as much as 12 mm. and 15 

 mm., respectively); lemmas pubes- 

 cent, sometimes sparsely so or sca- 

 brous only or pubescent only on the 

 margins at base. % — Dry or sand}^ 

 soil, British Columbia to Oregon. 



8. Agropyron riparium Scribn. and 

 Smith. Streambaxk wheatgrass. 

 (Fig. 312.) Resembling A. dasystachy- 

 um, with vigorous rhizomes; blades 

 usually narrower; spikelets usually 

 more imbricate; lemmas glabrous or 

 somewhat pubescent along the edges 

 of the lower part of the lemma. % 

 — Dry or moist meadows and hills, 

 North Dakota to Alberta and Wash- 

 ington, south to Oregon and Colorado. 



