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



6. Agropyron dasystachyum (Hook.) Scribn. Thickspike wheat- 

 grass. (Fig. 447, A) Often glaucous; culms mostly 40 to 80 cm tall, 

 with creeping rhizomes; blades flat to involute, 1 to 3 mm wide; 

 spike mostly 6 to 12 cm long; spikelets loosely to closely imbricate, 

 4- to 8-flowered, 1 to 1.5 cm long, the rachilla pubescent on the con- 

 vex side; glumes acute or awn-pointed, scabrous or pubescent (usually 



Figure 445.— Agropyron smithii, X 1. (Nelson 3918, Wyo.) 



less pubescent than the lemma), 6 to 9 mm long; lemmas densely to 

 sparsely pubescent, sometimes nearly glabrous, awnless or mucronate, 

 about 1 cm long; palea about as long as the lemma, obtuse. % — 

 Plains and sandy shores, Michigan to British Columbia, south to Illi- 

 nois, Nebraska, Colorado, northern Arizona, Nevada, and Oregon 

 (fig. 448). 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 polymorphous group. 



7. Agropyron elmeri Scribn. (Fig. 447, B.) 

 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 13 mm and 15 mm, respectively); lemmas pubes- 

 cent, sometimes sparsely so or scabrous only or pubescent only on the 

 margins at base. % — Dry or sandy soil, British Columbia to Orgeon. 



8. Agropyron riparium Scribn. and Smith. Streambank wheat- 

 grass. (Fig. 449.) Resembling A. dasystachyum, 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 Washington, south to Oregon, Arizona, and 

 Colorado (fig. 450). 



Figure 446.— Distribution of 

 Agropyron smithii. 



