MANUAL OF THE GRASSES OF THE UNITED STATES 425 



Lemma about 8 mm long, villous at summit, pubescent 



below 23. S. scribneri. 



Lemma about 5 mm long, villous all over but more so 



above 30. S. pinetorum. 



Hairs not copious, usually not more than 1 mm long at 

 summit. 

 Glumes broad, abruptly acuminate, rather firm, the first 



5-nerved 24. S. lemmoni. 



Glumes narrow, gradually acuminate, usually hyaline, 

 the first usually 3-nerved. 

 Awn 4 to 6 cm long, obscurely geniculate, the terminal 



segment flexuous 31. S. arida. 



Awn mostly less than 5 cm long, if as much as 4 cm 

 long, twice-geniculate and the terminal segment 

 straight or nearly so. 

 Sheaths, at least the lowermost, pubescent. 



29. S. WILLIAMSII. 

 Sheaths glabrous. 



Sheaths villous at the throat; fruit rather turgid, 



the callus broad and short; lower nodes of 



panicle villous. 



Glumes thin, papery; plants rather slender, 



mostly less than 1 m tall; panicle rather 



slender, open 25. S. viridula. 



Glumes firm, the nerves inconspicuous; plants 

 robust, mostly more than 1 m tall; panicle 



larger, more compact 26. S. robusta. 



Sheaths not villous at the throat or only slightly so; 

 fruit slender, the callus narrow, sharp-pointed; 

 nodes of panicle glabrous or nearly so. 

 Awn mostly more than 2 cm long; hairs at sum- 

 mit of lemma about as long as the others. 



27. S. COLUMBIANA. 



Awn mostty less than 2 cm long; hairs at summit 

 of lemma longer than those on the body 

 1 to 1.5 mm long 28. S. lettermani' 



1. Stipa neomexicana (Thurb.) Scribn. New Mexican feather- 

 grass. (Fig. 885.) Culms mostly 40 to 80 cm tall; sheaths glabrous 

 or the lower minutely pubescent; ligule very short, ciliate; blades 

 slender, firm, convolute, glabrous beneath, the basal 10 to 30 cm long, 

 scarcely 1 mm wide when unrolled; panicle narrow, 3 to 8 cm long; 

 spikelets pale, more or less shining; glumes 3 to 5 cm long, tapering 

 to a fine point; lemma about 15 mm long including the pilose callus 

 4 to 5 mm long; awn readily deciduous, 12 to 18 cm long, the lower 

 one-fourth to one-third straight, strongly twisted, appressed-villous, 

 the middle segment 1 to 2 cm long, the terminal segment flexuous, 

 plumose, the hairs about 3 mm long. % — Mesas, canyons, and 

 rocky slopes, western Texas and Colorado to Utah and Arizona (fig. 

 886). 



2. Stipa speciosa Trin. and Rupr. Desert needlegrass. (Fig. 

 887.) Culms numerous, 30 to 60 cm tall; sheaths brownish, smooth 

 or the lower pubescent or even felty at the very base, the throat 

 densely short- villous ; ligule short; blades elongate, involute-filiform, 

 mostly basal, more or less deciduous from the outer and older per- 

 sistent sheaths; panicle narrow, dense, 10 to 15 cm long, not much 

 exceeding the leaves, white or tawny, feathery from the plumose 

 awns; glumes smooth, 14 to 16 mm long, 3-nerved, long-acuminate, 

 papery; lemma 7 to 9 mm long, narrow, densely short-pubescent, the 

 callus sharp and smooth below; awn with one sharp bend, the first 

 section 1.5 to 2 cm long, densely long-pilose on the lower half or two- 

 thirds, the hairs 5 to 8 mm long, the remaining portion of the awn 



