MANUAL OF THE GRASSES OF THE UNITED STATES 



297 



sativa, A. Jatua (including A. orientalis Schreb.), A. nuda, A. sterilis, 

 A. byzantina (including A. sterilis var. algeriensis Trabut). 



SECTION 2. AVEN!STRUM Koch 



Perennials; spikelets upright, mostly less than 2 cm long. 



4. A vena pubescens Huds. (Fig. 588.) Culms erect, 50 to 80 cm 



tall; sheaths pubescent; blades flat, pubescent; panicle narrow, open, 

 10 to 15 cm long, the flexuous branches ascend- 

 ing; spikelets mostly 3-flowered, 12 to 15 mm 

 long, glumes and lemmas thin, shining, the 

 rachilla with long white hairs; first glume 1- or 

 3-nerved, the second 3-nerved; lemmas about 

 1 cm long; awn attached about the middle, 1.5 

 to 2 cm long. 01 Waste places, Connecticut 



FIGURE 586 -Distribution of an( j Vermont; introduced from Europe. 



./ic/c7iu JulUd, ^ A li^r^"i rv y-i-i 



5. Avena nooken Scnbn. SPIKE OAT. (Fig. 



589.) Culms densely tufted, 20 to 40 cm tall; blades firm, flat or 

 folded, 1 to 3 mm wide, the margins somewhat thickened; panicle 

 long-exserted, narrow, 5 to 10 cm long, the branches erect or as- 

 cending, 1-flowered, or the lower 2-flowered; spikelets 3- to 6-flowered, 

 about 1.5 cm long; glumes very thin, slightly shorter than the 

 spikelet; lemmas firm, brown, sca- 

 berulous, 1 to 1.2 cm long, the 

 callus short-bearded, the rachilla 

 joint white-villous ; awn 1 to 1.5 cm 

 long.^ 21 Dry slopes and prairies, 

 Manitoba to Alberta, Montana, and 

 New Mexico (fig. 590). 



6. Avena mortoniana Scribn. 

 ALPINE OAT. (Fig. 591.) Culms 

 densely tufted, 10 to 20 cm tall; 

 blades erect, firm, usually involute; 



FIGURE 587. Avena barbata. Spikelets, X 1; tip of FIGURE 588. Avena pubescens. Glumes and floret, 

 lemma, X 5. (Davy 5023, Calif.) X 5. (Weatherby and Harger 4249, Conn.) 



panicle short-exserted, purplish, narrow, 2 to 5 cm long, the short 

 branches erect, bearing usually a single spikelet, 10 to 12 mm long, 

 mostly 2-flowered; glumes exceeding . the florets; lemmas firm, 

 glabrous, the apex with 4 soft teeth, the callus with a tuft of stiff hairs 

 about 2 mm long, the rachilla long-villous ; awn 1 to 1.5 cm long. 

 21 Alpine meadows, Colorado, Utah, and New Mexico. 



