42 POACEAE 



18. STIPA L. Si'EAK Grass, Porcupine Grass, Devil's Darning- 

 needles. Feather Grass. 



Usually tufted perennials. Inflorescence paniculate. Spikelets narrow, 1- 

 flowered; flowers perfect. Empty glumes 2, narrow, persistent, keeled, acute, 

 rarely a\raed. Lemma narrow, strongly convolute, rigid, with a strong, usually 

 acute callus at the base and ending in a bent awn, which is spiralh" twisted below 

 the knee. Styles distinct, short; stigmas plumose. 



Outer glume of the spikelet 2 cm. long or more. 



Awn plumose. 1. S. neo-mexicana. 



Awn not plumose. 



Base of the panicle exserted: lemma more than 12 mm. lont;: awn straight above 

 the bend. 

 Lemma 20-2.5 mm. long. 2. S. spartea. 



Lemma 12-1.5 mm. long. 3. S. Tucediii. 



Base of the panicle usually included in the upper sheath: lemma S-12 mm. long; 

 awn slender and curled above the liend. 4. S. comata. 



Outer glume of the spikelet 1.5 cm. long or less. 



Panicle loose and open; branches spreading or reflexed. 



Awn plumose. 5. S. Porteri. 



Awn not plumose. 



Callus acute; lemma 7-8 mm. long. C. S. Richarclsonii. 



Callus short, bhmt; lemma about 4 mm. long. 7. S. canadensis. 



Panicle dense and spike-like. 



Awn glabrous, scabrous, or strigose, not plumose. 

 Lemma long-hairy towards the apex. 

 Lemma about 5 mm. long. 



Glumes green, rarely slightly tinged with purple; lemma nearly glab- 

 rous below. 8. S. Lettermanii. 

 Glumes purplish with paler margins; lemma pubescent throughout, 

 though more densely so above. 9. S. pinctnrum. 

 Lemma about 8 mm. long. 10. S. Scribneri. 

 Lemma equally hairy throughout. 

 Sheaths glabrous. 



Empty glumes scarious or hyaline; their nerves hence prominent. 



Lemma 4-6 mm. long, spindle-shaped when mature; callus short. 

 Stem-leaves broader than the basal leaves, often flat; sheaths 



with a ring of hairs at the tliroat. 11. S. ririclula. 



Stem-leaves as well as the basal leaves very narrow, involute; 

 sheaths glabrous. 

 Plant green; sheaths close; inflorescence distinctly exserted. 



12. S. Columbiana. 

 Plant pale and glaucous; sheaths loose; inflorescence included 

 or barely exserted; awn glabrous. 13. S. arida. 



Lemma 6-7 mm. long, almost cylindric; callus long and pointed. 



14. S. Nclsonii. 

 Empty glumes firm, thickish, herbaceous; the nerves not prominent. 



Lemma about 5 mm. long; leaf-blades narrow and involute. 



15. S. minor. 

 Lemma 8-10 mm. long; leaf-blades broad. 



Panicle slender; stem low and slender. 9. S. Scribneri. 



Panicle stout and dense; stem tall and stout. 16. S. Vaseyi. 

 Sheaths and lower leaf-blade pubescent. 17. S. Williamsii. 



Awns plumose or subplumose at least below. 



Hairs of the awns less than 1 mm. long; empty glumes 10-12 mm. long. 

 Ligules 1 mm. long or less. 



Sheaths, at least the lower ones, hairy. 18. S. Elmeri. 



Sheaths glabrous. 19. S. oregonensis. 



Ligules 2-4 mm. long. 20. S. Thurbcriana. 



Hairs of the a^vns 3-6 mm. long; empty glumes 15-18 mm. long. 



21. S. speciosa. 



1. S. neo-mexicana (Thurb.) Va.sey. Tufted perennial; stem erect, smooth, 

 3-10 dm. high; basal leaf-blades 2-3 dm. long, strongly involute, those of the 

 stem-leaves shorter; panicle narrow, 1-1.5 dm. long; branches erect, with 1-3 

 spikelets; empty glumes lanceolate, 3-4.5 cm. long; lemma strigose, 10-15 mm. 

 long; awn 1-1.5 dm. long, plumose, twisted for one-third its length, twice bent; 

 callus long and sharp. S. pennala 7ieo-inexicaria Thiirb. Dry hills: Tex. — 

 Colo. — Utah — Calif. Son. — Submont. My-Au. 



2. S. spartea Trin. Tufted perennial; stem 6-15 dm. high, erect, simj^le; 

 basal leaf-blades 2-5 dm. long, usually involute, scabrous above; stem-leaves 

 1.5-3 dm. long, usually flat; panicle 1-2.5 dm. long; outer glumes of spikelets 

 2.5-3.7 cm. long, acuminate, awn-pointed, glabrous; callus long, sharp; awn 12- 

 20 cm. long. Prairies: Man.— 111.— N.M.— B.C. Plain—Suhmont. Je-Au. 



