Spikelets hermaphrodite, usually 1-flowered. Glumes 4, the outer 3 membranous, 

 the third often subtending a hyaline palea and rarely a staminate flower, the 

 fourth or flowering glume chartaceous, smooth or transversely rugose, inclosing 

 a palea of similar texture. Stamens 3. Styles distinct, elongated; setje persist- 

 ent, single or in clusters below the articulation of the raehilla; stigmas plumose. 

 Grain free, inclosed within the glimies and palea. 



Annual or perennial grasses with erect culms, flat leaves, and dense, cylindrical, or 

 some\\hat open bristly panicles. 



Species about 40 in the tropical and more temperate regions of both hemispheres. 



ANALYTICAL KEY TO THE SPECIES. 



1. Setfe 5 to 16 at the base of each spikelet, involucrate 2 



1. Setfe 1 to 3 at the base of each spikelet, not involucrate 5 



2. Annual; setpe short, tawny-yellow 1 C. glauca. 



2. Perennial, from short creeping rootstocks 3 



3. Seta; short, once or twice as long as the spikelets; panicles slender 4 



3. Seta; generally elongated, spreading; panicles thick 2 C. imberbis. 



(rt) Setae very long, yellow or purple var. penicillata. 



(h) Plants not cfespitose; culms naked and wiry at the base; spikelets purplish 



var. perennis. 



(c) Plants robust, glaucous; culms erect; leaves long, rigid, erect; panicles pale 



green, elongated var. streptobotrys. 



(fZ) Plants robust; culms geniculate; panicles 6 to 12 cm. long, yellowish 



var. g-eniculata. 



4. Leaves narrow, linear, elongated; panicle very slender, pale 4 C. gracilis. 



4. JLeaves linear-lanceolate, short; panicle thicker, usnially purplish 



3 C. purpurascens. 



5. Second glume equaling the flowering glume in length 6 



5. Second glume shorter than the flowering glume 15 



6. Setae antrorsely scabrous 7 



6. Setae retrorsely scabrous, wholly or in part 13 



7. Flowering glmne strongly transversely undulate-rugose 12 C. longipila. 



7. Flowering glume smooth, or at least only punctate or striate, not rugose 8 



8. Panicle dense, cylindrical; branches short, approximate, densely flowered... 9 



8. Panicle lax; branches remote, generally elongated, few-flowered 12 



9. Flowering glume very smooth, glossy; plants robust, 18 to 36 dm. high 



11 C. magna. 



9. Flowermg glume more or less roughened, not glossy; plants less than 18 dm. 

 high 10 



10. Axis of the inflorescence scabrous; branches subverticillate 8 C. ambigua. 



10.' Axis of the inflorescence pilose; branches alternate 11 



11. Panicles 2 to 8 cm. long, 1 cm. or less thick; spikelets 2 mm. long, much exceeded 



by the usually green setae - 9 C. viridis. 



11. Panicles 5 to 20 cm. long, 1 to 3 cm. thick; spikelets about 2.3 mm. long, 



equaled or exceeded by the usually purple setae; cultivated 10 C. italica. 



(a) Culms 3 to 9 dm. high; panicle 1 cm. in diameter; setae long, purple, rarely 

 crreen var. germanica. 



12. Spikelets 3 mm. long 24 C. villosissima. 



12. Spikelets 2 mm. long 25 C. grisebachii. 



13. Setae retrorsely scabrous above, antrorsely scabrous at the base; leaves pubes- 



cent 7 C. scandens. 



13. Setae retrorsely scabrous throughout; leaves scabrous 14 



14. Panicles 1.5 to 3 cm. long, 1 cm. thick, purplish 5 C. ■brevispica. 



