MANUAL OF THE GRASSES OF THE UNITED STATES 



437 



29. Stipa williamsii Scribn. Williams needlegrass. (Fig. 928.) 

 Differing from S. columbiana chiefly in having more or less pubescent 

 culms, sheaths, and blades; culms 60 to 100 cm tall; panicle 10 to 20 

 cm long; lemma about 7 mm long; awn usually 3 to 5 cm long. 91 — 

 Dry hills and plains, Montana to Washington, south to Colorado and 

 California (fig. 929). 



30. Stipa pinetorum Jones. (Fig. 930.) Culms in large tufts, 30 

 to 50 cm tall; ligule very short; leaves mostly basal, the blades 5 to 



12 cm long, involute-filiform, more or less 

 flexuous, slightly scabrous; panicle narrow, 8 to 

 10 cm long; glumes about 9 mm long; lemma 5 



Figure 929.— Distribution of 

 <S£i'pa williamsii 



Figure 928.— Stipa 

 williamsii. Floret, 

 X 1; lemma, X 5. 

 (Williams 2804, 

 Wyo.) 



Figure 930.— Stipa 

 pinetorum. Floret, 

 X 1; lemma, X 5. 

 (Jones 6023, Colo.) 



mm long, narrowly fusiform, clothed especially on the upper half with 

 hairs 2 mm long, forming a conspicuous tuft exceeding the body of the 

 lemma; awn about 2 cm long, twice-geniculate, nearly 

 glabrous. 91 — Open pine woods at high altitudes, rare, 

 Colorado, Utah, Nevada, and California (fig. 931). 



31. Stipa arida Jones. (Fig. 932.) Culms 40 to 80 

 cm tall; blades 10 to 20 cm long, 1 to 2 mm wide, flat or 

 involute, scabrous; panicle 10 to 15 cm long, narrow, 

 compact, pale or silvery; glumes 8 to 12 mm long; lemma 



about 5 mm long, appressed-pubes- 

 cent on the lower half and along the 

 margin, slightly roughened toward 

 the summit; awn 4 to 6 cm long, 

 capillary, scaberulous, loosely 

 twisted for 1 or 2 cm, flexuous be- 

 yond. 91 — Rocky slopes, rare, 

 southwestern Colorado, Utah, and 

 Arizona. 



32. Stipa tenuissima Trin. (Fig. 933.) Culms in 

 large tufts, slender, wiry, 30 to 70 cm tall; ligule 2 mm 

 long; blades 15 to 30 cm long, sometimes longer, filiform, 

 wiry, closely involute; panicle 10 to 30 cm long, narrow, 

 soft, nodding; glumes about 1 cm long; lemma 2 to 3 mm 

 long, oblong-elliptic, glabrous, minutely papillose-rough- 

 ened, the short callus densely pilose; awn about 5 cm long, capil- 

 lary, flexuous, obscurely geniculate about the middle. 91 — Dry open 

 ground, rocky slopes, and open dry woods, Texas and New Mexico 

 to central Mexico; Argentina. 



Figure 931.— Distribution of 

 Stipa pinetorum. 



Figure 932.— 

 Stipa arida. 

 Floret, X 1; 

 lemma, X 5. 

 (Jones 5377, 

 Utah.) 



