MANUAL OF THE GRASSES OF THE UNITED STATES 



447 



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



32. S. PINETORUM. 



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

 Glumes broad, abruptly acuminate, rather firm, the first 5-nerved. 



25. S. LEMMONI. 

 Glumes narrow, gradually acuminate, usually hyaline, the first usu- 

 ally 3-nerved. 



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

 flexuous 33. 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. 



30. 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, loose. 



26. S. VIRIDULA. 

 Glumes firm, the nerves inconspicuous; plants robust, 



mostly more than 1 m. tall; panicle larger, more com- 

 pact 27. S. ROBUSTA. 



Sheaths not villous at the throat or only slightly so; fruit 

 slender, the callus narrow, sharp-pointed; nodes of pan- 

 icle glabrous or nearly so. 

 Culms densely pubescent below the nodes. 



31. S. DIEGOENSIS. 

 Culms glabrous throughout. 



Awn mostly more than 2 cm. long; hairs at summit of 

 lemma about as long as the others. 



28. S. COLUMBIANA. 



Awn mostly less than 2 cm. long; hairs at summit of 

 lemma longer than those on the body, 1 to 1.5 mm. 



long 29. S. LETTERMANI. 



(Thurb.) 



FEATHER- 



1. Stipa neomexicana 



Scribn. New Mexican 

 grass. (Fig. 638.) 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 

 10 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 cal- 

 lus 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, plu- 

 mose, the hairs about 3 mm. long. 

 % — Mesas, canyons, and rocky 

 slopes, western Texas, Oklahoma, 

 Wyoming, and Colorado to Utah and 

 Arizona. 



Figure 



638. — Stipa neomexicana. Plant, 

 lemma, X 5. (Jones 5377, Utah.) 



X V*\ 



