8 



14. Panicles 5 to 18 em. long, tapering to xhe obtuse apex, green, rarely pur- 



plish 6 C. verticillata. 



15. Spikelets 3 mm. long 16 



15. Spikelets less than 3 mm. long 18 



16. Leaves smooth or scabrous 17 



16. Leaves pilose-pubescent 24 C. villosissima. 



17. Leaves lanceolate, 10 to 20 mm. wide; panicle loose; branches elongated, few- 



flowered 23 C. macrosperma. 



17. Leaves linear, glaucous, 2 to 5 mm. wide; panicle subspiciform; branches densely 



flowered 18 C. composita. 



18. Inflorescence spike-hke, dense ; branches very short, approximate 19 



18. Inflorescence lax, mterrupted ; branches more or less elongated 24 



19. Flowering glume strongly transversely imdulate-rugose 20 



19. Flowering glume smooth or only finely transversely wrinkled 23 



20. Leaves smooth or scabrous 13 C. corrugata. 



(a) Spikes 5 to 7 cm. long; setee usually purplish, spreading. . var. parviflora. 



20. Leaves pubescent or pilose ! 21 



21. Leaves lanceolate, acute, 12 to 15 mm. wide; set« long 21 C. latifolia. 



(a) Leaves 10 mm. wide or less; setae short var. breviseta. 



21. Leaves linear or linear-lanceolate, about 5 mm. wide 22 



22. Culms pilose with scattered hairs ; fertile palea nearly plane 15 C. hispida. 



22. Culms smooth ; fertile palea strongly convex 14 C. gibbosa. 



23. Leaves pilose ; plants 2 to 3 dm. high 16 C. leucopila. 



23. Leaves smooth or scabrous, glaucous'; plants robust, 4 to 9 dm. high 



18 C. composita. 



24. Seta3 antrorsely and more sparingly retrorsely scabrous 17 C. onurus. 



24. Setae antrorsely scabrous only 25 



25. Flowering glume very strongly transversely undulate-rugose 26 



25. Flowering glume smooth or only finely transversely wrinkled 27 



26. Leaves and rachis pilose 21 C. latifolia. 



26. Leaves and rachis scabrous 22 C. liebmanni. 



(a) Branches of the panicle very short ; leaves 1 dm. long or less, 8 to 10 

 mm. wide var. pauciflora. 



27. Leaves hnear 28 



27. Leaves lanceolate or linear-lanceolate 29 



28. Leaves glaucous; panicle pale, obtuse at the apex. 18 C. composita. 



28. Leaves pubescent; panicle long-attenuate at the apex 27 C. caudata. 



29. Panicle subcylindrical ; branches densely flowered 30 



29. Panicle more lax; branches loosely few-flowered 31 



30. Margins of the sheaths smooth; setae short 20 C. rigida. 



30. Margins of the sheaths ciUate-f ringed; setae long, spreading 



19 C. macrostachya. 



31. Flowering glume manifestly transversely wrinkled 32 



31. Flowering glume smooth or only pitted or striate 25 C. grisebachii. 



(o) Plants densely csespitose, less than 1 dm. high var. mexicana. 



(6) Plants robust, 5 to 8 dm. high; branches of the panicle elongated, spreading, 

 the lower ones 2 to 3.5 cm. long var. ampla. 



32. Panicle long-attenuate at the apex; branches strict, erect; leaves pubescent 



28 C. setosa. 



32. Panicle obtuse at the apex; branches spreading; leaves smooth or pilose 



26 C. polystachya. 



