38 POACEAE 



beneath, 2-3 mm. wide, the upper usually 8-14 cm. long; panicle much exserted, 

 4-6 cm. long, its branches nearly erect; spikelets about 3.25 mm. long and 1.5- 

 1.75 mm. wide; first empty glume ovate, one-third as long as the spikelet. Prair- 

 ies and hills: Ind. Okla. (Black Hills) S.D. Plain Submont. My-Jl. 



10. P. Wilcoxianum Vasey. Cespitose perennial, tufted; stems 1-2.5 dm- 

 high, sparingly pilose with long white hairs; sheaths papillose-pilose; leaf -blades 

 3.5-7.5 cm. long, less than 4 mm. wide, pubescent with long hairs; panicle 3-4 

 cm. long, ovoid, flexuose; spikelets about 2.5 mm. long, ellipsoid; first glume 

 ovate, about one-fourth as long as the spikelet; second and third glumes pubes- 

 cent. Prairies: S.D. Kans. Ore. Plains. Je-JL 



11. P. Scribnerianum Nash. Somewhat cespitose perennial; stem erect, 

 1.5-6 dm. high, simple or later dichotomously branched, sparingly hairy; sheaths 

 strongly papillose-hirsute; leaf-blades 5-10 cm. long, 6-12 mm. wide, glabrous 

 and smooth above, scabrous and sparingly hairy beneath; primary panicle 

 ovoid, 3.5-7.5 cm. long, the secondary ones much smaller and more or less in- 

 cluded; spikelets obovoid, 3 mm. long; first glume ovate, one-fourth as long as 

 the spikelet; second and third glumes glabrous or finely pubescent. Panicum 

 scoparium S. Wats., not Lam. Meadows: Me. Va. Ariz. Ore. B.C. Plain 

 Submont. My-Jl. 



12. P. obtusum H.B.K. Perennial, with a more or less tufted rootstock, 

 producing creeping stolons; stem compressed, 2-8 dm. high, decumbent at the 

 base, glabrous; leaf -blades 3-20 cm. long, 2-7 mm. wide, involute towards the 

 tip, glabrous or nearly so; panicle short-exserted, 3-12 cm. long; spikelets short- 

 pedicelled, 3-4 mm. long, obovoid, glabrous; first glume nearly as long as the 

 spikelet; second and third glumes subequal; third glume often enclosing a stam- 

 inate flower. Brachiaria obtusa (H.B.K.) Nash. Sandy and gravelly soil: 

 Mo. Tex. Ariz. Colo.; Mex. Son. 



11. ECHINOCHLOA Beauv. BARNYARD GRASS, JUNGLE RICE. 



Coarse and often tall annuals. Inflorescence of several unilateral spikes or 

 racemes. Spikelets 1- or 2-flowered, crowded in small clusters or racemes, in 

 two rows on one side of the flat rachis. Empty glumes 3, membranous, hispid, 

 the first much shorter than the spikelet; all awned or awn-pointed. Lemma 

 chartaceous, glabrous and shining, indurate, acute or acuminate, enclosing a 

 shorter palet. Styles distinct; stigmas plumose. 



1. E. Crus-galli (L.) Beauv. Stem 4-12 dm. high, branched at the base; 

 leaf -sheaths keeled; blades 1.5-4 dm. long, 6-10 mm. wide, glabrous, smooth; 

 panicle of 5-15 secund branches; spikelets ovate, crowded in 2-4 rows, about 4 

 mm. long, hispidulous, hispid on the nerves; first glume broadly ovate, nearly 

 half as long as the rest; the third glume in the typical form usually with an awn 

 4-10 mm. long, but in the native form of the Rocky Mountain region (var. 

 mutica] usualty all merely cuspidate. Panicum Crus-galli L. Wet places, culti- 

 vated ground and waste places: N.S. Fla. Calif. Wash.; Mex., W. Ind., 

 Eurasia. Plain Submont. Je-O. 



12. CHAETOCHLOA Scribn. FOXTAIL GRASS. 



Annuals or perennials. Inflorescence of dense terminal cylindric spike-like or 

 narrowly thyrsoid panicles. Spikelets in a cluster of 1-several sterile, barbed 

 bristle-like persistent branches. Empty glumes 3, membranous, the first often 

 very short and together with the larger second one empty, the third glume fre- 

 quently longer than the second, empty, or rarely enclosing a palet and also some- 

 times a staminate flower, the lemma usually shorter than the spikelet, chartaceous, 

 glabrous, shining, often transversely rugose, finally indurated, obtuse, enclosing 

 a shorter palet. Styles distinct, elongated: stigmas plumose. [Setaria Beauv.] 



Inflorescence with the spikelets racemosely arranged; bristles 5-16 at the base of each 



spikelet, involucrate, tawny-orange. 1. C. glauca. 



Inflorescence with the spikelets in clusters on the branches; bristles 1-3 at the base of 



each spikelet, not involucrate. 

 Second glume of the spikelet as long as the lemma, or very nearly so; annuals. 



Panicle usually 1 cm. thick or less; bristles commonly green; spikelets about 2 

 mm. long. 2. C. viridis. 



