46 GRAMINEAE (GRASS FAMILY) 



basal bristles single or in clusters below the articulation of the rachilla, and 

 therefore persistent. Glumes of the spikelet 4, the other three membranous, 

 the third often subtending a palet and rarely a staminate flower; inner or 

 fourth chartaceous, subtending a palet of similar texture and a perfect flower. 

 Stamens 3. Styles distinct, elongated; stigmas plumose. Grain free, in- 

 closed in the lemmas. Setaria. 



Annual; panicle dense . . . . . . . . . . 1. C. viridis. 



Perennial; panicle more or less interrupted . . . . . . 2. C. composita. 



1. Chaetochloa viridis (L.) Scribn. U. S. Dept. Agr. Div. Agros. Bull. 4: 39. 

 1897. Erect glabrous caespitose annuals, 2-9 dm. high: leaves 7-25 cm. long, 

 4-12 mm. wide: spikes compound, 3-10 cm. long: spikelets about 3 mm. long, 

 elliptic, much shorter than the green or sometimes yellowish bristles; first 

 glume less than one half as long as the spikelet, 1-3-nerved ; second and third 

 glumes obtuse, 5-nerved; fourth glume equaling or slightly exceeding the 

 second. GREEN FOXTAIL. Introduced into cultivated grounds and waste 

 places. 



2. Chaetochloa composita (H.B.K.) Scribn. U. S. Dept. Agr. Div. Agros. 

 Bull. 4: 39. 1897. Pale glaucous caespitose perennial, 3-10 dm. high, much 

 branched from the base: culms scabrous and often pubescent, rarely glabrous, 

 the nodes bearded with a ring of silky appressed hairs: leaves 10-25 cm. long, 

 2-5 mm. wide, scabrous on both sides or sometimes nearly glabrous: spikes 

 usually more or less interrupted, 5-16 cm. long: spikelets 2 or rarely 3 mm. 

 long, narrowly ovate, acute, much shorter than the single or rarely paired, 

 green, flexuous bristles; first glume one half as long as the spikelet, 3-nerved; 

 second and third glumes acute or apiculate, 5-nerved; fourth glume slightly 

 exceeding the second. Setaria setosa caudata. Southwestern Colorado. 



12. CENCHRUS L. SAND BUR 



Annuals or perennials, usually with flat leaves. Spikelets 1-4 together in 

 terminal spikes or racemes, subtended by a spiny involucre which is deciduous 

 with them at maturity. Glumes 4; the first hyaline; the second and third 

 membranous, the latter sometimes having a palet and staminate flower in its 

 axil; the fourth chartaceous, subtending a palet of similar structure which 

 incloses a perfect flower. Stamens 3. Styles united below; stigmas plumose. 

 Grain free, inclosed in the lemmas. 



1. Cenchrus tribuloides L. Sp. PL 1050. 1753. Culms erect or decumbent 

 from an annual root, 2-5 or more dm. high: sheaths usually loose, com- 

 pressed, smooth: leaves 6-12 cm. long: spikes 2-6 cm. long, sometimes par- 

 tially included in the upper sheath: involucres crowded on the scabrous rachis, 

 2-flowered, globose, pubescent except at the base, forming spiny burs, the 

 spines stout: spikelets about 6 mm. long. Sandy fields and waste grounds; 

 extending into our range from the eastern and southern United States. 



13. HOMALOCENCHRUS Mieg. 



Marsh grasses with flat, narrow, generally rough leaves and paniculate in- 

 florescence. Spikelets 1-flowered, perfect, strongly flattened laterally, and 

 usually more or less imbricated. Glumes 2, chartaceous, the outer one broad 

 and strongly coriduplicate, the inner much narrower. Stamens 1-6. Styles 

 short, distinct; stigmas plumose. Grain ovoid, free. 



1. Homalocenchrus oryzoides (L.) Poll. Hist. PI. Palat. 1: 52. 1776. 

 Rather stout rough much-branched perennial, 3-12 dm. high: leaves 7-25 cm. 

 long, 4-10 mm. wide: terminal panicle 12-22 cm. long, finally long-exserted, 

 its branches lax, and later widely spreading; lateral panicle generally included: 

 spikelets 4-5 mm. long, about 1.5 mm. wide, elliptic; glumes pubescent, the 

 outer one hispid on the keel and on the margins: stamens 3. RICE CUT-GRASS. 

 In swamps and along streams in the eastern part of our range; rare. 



