56 POACEAE 



Awn of the lemma geniculate, exserted; callus-hairs usually much shorter than the glume. 

 Awns of the lemma greatly exceeding the empty glumes; plant tufted; leaf-blades 



involute. 



Empty glumes very scabrous throughout; marcescent basal leaf-sheaths very 



long, loose and numerous. 1. C. purpurasccns. 



Empty glumes nearly glabrous, except on the keels; marcescent basal leaf-sheaths 



short and few. 2. C. Vaseyi. 



Awns of the lemma about equalling the empty glumes. 



Empty glumes sharply keeled; spikelets strongly compressed; plant stoloniferous. 



3. C. montanensis. 

 Empty glumes not strongly keeled; spikelets not strongly conpressed; plants 



tufted. 

 Leaves usually involute; panicle very dense. 



Panicle verj narrow, spike-like, usually red-purplish. 4. C. rubescens. 

 Panicle lance-oblong, usually pale green. 5. C. Suksdorfii. 



Leaves usually flat; panicle ovoid, open. 6. C. luxurians. 



Awn of the lemma straight or nearly so, included; callus-hairs usually equalling the 



lemma (except in C. scopulorum and C. Cusickii). 

 Panicle open, the lower branches spreading; leaf-blades usually flat; callus-hairs 



nearly or quite equalling the lemma. 



Empty glumes 4-6 mm. long, narrow, sharp-acuminate; awn of the lemma at- 

 tached below the middle, exceeding the lemma. 7. C. Lanqsdorfli. 

 Empty glumes 2-4 mm. long; awn of the lemma attached at or above the middle, 



shorter than the lemma. 



Awn attached near the middle of the lemma; spikelets usually purple. 

 Spikelets 3-4 mm. long; panicle loosely flowered. 8. C. canadensis. 



Spikelets 2-2.5 mm. long; panicle densely flowered. 9. C. Macouniana. 

 Awn attached near the apex of the lemma; spikelets pale or white. 



10. C. blanda. 



Panicle more or less contracted. 

 Leaf-blades flat or nearly so. 



Empty glumes smooth or nearly so, except on the veins. 



Callus-hairs copious, at least two-thirds as long as the lemma; plant with 



a rootstock. 11. C. Scribncri. 



Callus-hairs sparse, much shorter than the lemma. 



Plant tall, 9-12 dm. high; sheaths bearded at the summit; plant with a 



rootstock. 12. C. Cusickii. 



Plant lower, 3-8 dm. high; sheaths not bearded; plant tufted. 



13. C. scopulorum. 



Empty glumes verj scabrous; plant tufted. 14. C. elongata. 



Leaf-blades strongly involute. 



Panicle open. 15. C. lucida. 



Panicle dense, narrow, spike-like. 



Spikelets 2 mm. long; empty glumes thickish, barely acute or obtusish. 



16. C. micrantha. 

 Spikelets 3-4.5 mm. long. 



Plant scarcely cespitose; empty glumes long-acuminate. 



Leaves filiform, soft; plant 4-6 dm. high, slender; empty glumes 



minutely scabrous on the veins. 17. C. neglecta. 



Leaves stiff and hard; plant 8-12 dm. high; empty glumes strongly 



scabrous. 18. C. inexpansa. 



Plant densely cespitose; empty glumes abruptly acute or short-acumin- 

 ate, very scabrous. 19. C. americana. 



1. C. purpurascens R. Br. Tufted perennial; stem 3-6 dm. high; leaves 

 numerous and crowded at the base; blades of the basal leaves 2-4 dm. long, 

 4-5 mm. wide, scabrous, rigid, more or less involute; those of the stem 7-15 cm. 

 long; panicle spike-like, strict, 7-10 cm. long, purplish; spikelets 6-7 mm. long; 

 lemma slightly shorter than the glumes, acute or acuminate; awn near the base, 

 twisted below and bent at the middle. Mountains: Greenl. S.D. Colo.- 

 Calif. Alaska. Mont. Alp. Jl-S. 



2. C. Vaseyi Beal. Tufted perennial; stem 3-7 dm. high, leafy; leaf-blades 

 1.5-2 dm. long, 3-7 mm. wide, the lower involute, the upper often flat; panicle 

 spike-like, 7-10 cm. long, usually more or less purple; empty glumes 4-5 mm. long, 

 equal, lanceolate; lemma one-fourth shorter, obtuse; awn inserted one-third 

 from the base and extending little beyond the empty glumes. Mountains: Ore. 



-Wash. Mont. Alp. Subalp. Jl-Au. 



3. C. montanensis Scribn. Stoloniferous perennial; stem 2-4 dm. high, 

 stiff, erect; leaf-blades' 5-15 cm. long, strongly involute, scabrous; panicle spike- 

 like, 5-8 cm. long, dense; empty glumes narrowly lanceolate, acute, 4-6 mm. 

 long, scabrous, pale or purple; lemma one-fourth shorter, thin, finely scabrous, 

 awn borne one-third from the base. Dry plains: Sask. S.D. Ida. Alta. 

 Plain Submont. Jl-Au. 



