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, 

 tin- thin! 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, m- 

 in the lemmas.. 



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



IVrrnniul; panicle more or less interrupted ...... J. U composita. 



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

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

 -1 -12 nun. wide: spikes compound, 3-10 cm. long: spikelets about 3 mm. long, 

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

 glume Jess 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. 



i>. 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- 

 1, 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-f lowered, 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- 



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



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



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



>hort, di-tinei; stigmas plumose. Grain ovoid, free. 



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



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



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



Hid later widely spreading; lateral panicle generally included: 



-pikelets 1 r, mm. long, about l.r> mm. wide, elliptic-; glumes pubescent, the 



OUter One hispid on the keel and on the margins: stamens 3. RICE CliT-GRASS. 



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



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