171 



Fig. 165. AVENA AMERICANA Scribn. U. S. Dept. Agr. Div.Agros. Bui. 7: 

 183, fig. 165. 1897. {A.pmtensis var. Americana Scribn. Bot. Gaz. 11: 177. 1886; 

 A. hookeriScnhn. in Hack. True Grasses, 123. 1890.) AMERICAN OAT-GRASS.— A 

 rigidly erect perennial 3-6 dm. (l°-2°) high, with narrow, firm leaves, and con- 

 tracted panicles 8-12 cm. (3'-5') long. Sheaths exceeding the internodes; ligule 

 obtuse, hyaline, abovit -1 mm. (2") long; leaf-blades rigid 5-15 cm. (2'-6') long, 

 2-5 mm. (l"-2^") wide, acute or obtuse. Spikelets (a) about 14 mm. (7") long, 4- 

 to5-flowered; empty glumes lanceolate, about as long as the spikelet, slightly 

 scabrous on the keel; flowering glumes about 12 mm. (6") long, smooth, the awn 

 attached near the middle, geniculate, twisted below, scabrous.— Open thickets 

 and prairies, Manitoba, and in the foothills of the Rocky Mountains south- 

 ward to Colorado. June to August. 



