14 



6. Leaves of innovations long, often equaling or surpassing the -whitish panicle, 



plant rather rigid 5. C. howellii. 



7. Innovations extravaginal, rootstock strong, creepiug, spikelets 4 to 5 iiun. long 



3. C. lemmoni. 



7. Innovations iutravagiual, rootstock none, spikelets 3.5 to 4 mm. long 



4. C. breweri. 



8. Strongly c;xjspitose, rather hard iu texture, leaf-blades strongly involute 9 



8. Not Cicspitose, soft iu texture, leaf-blades flat 9. C. tweedyi. 



9. Innovation leaves very long (often surpassing the culm), tiliform, not rigid, 



spikelets 8 to 10 mm. long 6. C, foliosa. 



9. Innovation leaves short, not filiform, somewhat rigid, spikelets 4 to 8 mm. long. 10 



10. Marcescent basal sheatLis closelj' investing culm for }, to J its length, panicle 



very dense, empty glumes more or less scabrous all over. . 7. C. purpurascens. 



10. Marcescent basal sheaths nnich shorter, loose, panicle somewhat interrupted, 



empty glumes nearly glabrous except on keel 8. C. vaseyi. 



11. Panicle open, loosely flowered, the rays wide-spreading 12 



11. Panicle contracted, usually densely flowered, the rays erect or nearly so 13 



12. Plant low (1.5 to 3 dm.), soft, panicle dark purple, few-flowered, empty glumes 



not sharply keeled 2. C. deschampsioides. 



12. Planttall, rather hard, panicle pale, empty glumes shar]>ly keeled. 11. C.alentica. 



13. Spikelets strongly compressed, empty glumes sharply keeled 14 



13. Spikelets not stronglj' compressed, empty glumes not strougly keeled 19 



14. Plant low (not exceeding 5 dm.), leaves short, almost filiform, rigid, erect. 



Eocky Mountain species 10. C. montaueusie. 



14. Tall, leaves longer and wider. Pacific coast species 15 



15. Panicle narrow and dense, spike-like, leaves all strongly involute 16 



15. Panicle wider, not spike-like, usually loosely flowered, leaves often fiat 



11. C.alentica. 



16. Plant yellowish, sheaths not bearded at summit 17 



16. Plant not yellowish, sheaths bearded at summit 18 



17. Culms and sheaths strongly twisted toward base, panicle obhmg-lanceolate, not 



interrupted, spikelets 5 to 5.5 mm. hmg 12. C. vilfaeforniis. 



17. Culms and sheaths not or but slightly twisted, panicle oblong, much interrupted 



toward base, spikelets 4.5 to 5 mm. long 13. C. koelerioides. 



18. Panicle strict, spikelets about 6 mm. long 14. C. augusta. 



18. Panicleusuallysomewhatflexuous, spikelets 4 to 5mm. long. 15. C. subflexuosa. 



19. .More or less ca-spitose, culms usually rather rigid, leaf-blades usually involute. 



Kocky Mountains and westward 20 



19. Not crespitose, culms not rigid, leaf-blades usually flat. Eastern species 22 



20. Lower leaves in a dense tuft, short, rather rigid, strongly involute, si)ikelets 



about 4 mm. long 16. C. fasciculata. 



20. Lower leaves rarely forming a dense tuft, usually elongated, not rigid 21 



21. Panicle narrow, spiciform, usually red-piirple 17. C. rubescens. 



21. Panicle wider, rarely spicifurm. usually ])ale-green 18. C. suksdorfii. 



22. Sheaths rarely bearded at summit, panicle more or less tinged with lurid purple, 



empty glumes rather thick 19. C. breviseta. 



22. Sheaths usually bearded, panicle not lurid purple, empty glumes thin 23 



23. Spikelets 4 to 6 mm. long, callus hairs very sparse, the longer ^ to '. as long as 



glume, jialea e(|ualing or very nearly ef^ualing glume 20. C. porteri. 



23. Spikelets 3.5 to 4 mm. long, callus hairs rather copious, the longer about J as 



long as glume, palea considerably slnu-ter than glume 21. C. nemoralis. 



21. Panicle open, the lower rays wide-sjireadiug. leaf-blaihsllat, callus hairs copious, 

 nearly or cjuite equaliug glume 25 



24. Panicle more or less contracted 28 



25. Spikelets 4 to 6 mm. long, empty glumes narrow. ><harp-acuminate, awn stout. 



attached below middle, considerably exceeding glume.... 22. C. langsdorffii. 



