GRASS FAMILY 35 



2. P. mutica Buckl. Stems 2-6 cm. high, smooth and glabrous; blades 

 3-10 cm. long, involute, scabrous; spikes dense, 3-6 cm. long, 5-12 mm. thick; 

 spikelets usually overlapping; lower glumes of the middle spikelet narrow, 

 keeled, bearing 5-6 bristles; those of the lateral spikelets 4-5 mm. long, cuneate, 

 the outer one 6-9-nerved with a rounded scarious margin, the inner 4-nerved 

 with a short awn. H. mutica Benth. Tobo.sa Grass. Dry pfciins: Tex. — 

 Colo. — Ariz.; Mex. Son. Ajj-S. 



3. P. Jamesii Torr. Stem slightly hairy at the nodes, otherwise scabrous 

 or smooth, 1.5-4 dm. high; blades 1-15 cm. long, glaucous and scabrous, usually 

 revolute; spikes 5-8 cm. long, often purple-tinged; glumes of the middle spikelet 

 keeled, ciliate, 2-cleft, with 3-7 bristles on the back; lower glume of the lateral 

 spikelets 6-7 mm. long, awned above the middle; upper glume emarginate, cuspi- 

 date. H. Jamesii Benth. Galleta Grass. Hills and plains: Tex. — Wyo. — 

 Nev. — N.:M. Plain — Submont. — Son. ]\Iy-Au. 



7. PASPALUM L. Paspalum. 



Usually perennials with rootstocks. Inflorescence of one or more unilateral 

 racemes; spikelets 1-flowered, arranged singly or in pairs alternately in two rows 

 on one side of a flattened and more or less winged rachis. Glumes 2, rarely 3, 

 membranous. Lemma glabrous and shining, convex, with its back turned to- 

 wards the rachis, at last indurate. Styles distinct, long; stigmas plumose. 



1. P. stramineum Xash. Stem 2-8 dm. high; sheaths all but the lowest ones 

 glabrous, except the ciliate margins; blades yellowish-green, long-ciliate on the 

 margins, 5-25 cm. long, 5-10 mm. wide; racemes 4-10 cm. long, usually in pairs; 

 spikelets in pairs, orbicular, 2 mm. broad; first glume 3-nerved, pubescent; second 

 glume 2-nerved, glabrous or nearly so. P. setaceum A. Nels., not Michx. Sandy 

 places: Neb. — Okla. — Colo. Plain. Jl-S. 



8. SYNTHERiSMA Walt. Crab-grass. 



Annual grasses. Inflorescence composed of spike-like racemes, which are 

 disposed in whorls, or approximate at the summit of the stems. Spikelets nar- 

 row, acute, in 2's or 3's on one side of the fiat and winged or triangular rachis, 

 one of the spikelets generally longer-pedicelled than the rest. Glumes mem- 

 branous, the first small or wanting, the lemma chartaceous, glabrous and shin- 

 ing, at length indurated, enclosing a palet. Styles distinct; stigmas plumose. 

 [Digitaria Scop., not Heist.] 



Pedicels terete or nearly so, sparingly if at all liispldulous ; lower sheaths glabrous; lemma 

 brown in fruit. 

 Spikelets more than 2 mm. long. 1. S. Ischnemurn. 



Spikelets 1.2.5-1.5 mm. long. 2. S. paniceum. 



Pedicels sharply 3-angled, the angles strongly Iiispidulous, as also the sheath; lemma 

 white in fruit. 

 Spikelets about 2.5 mm. long; third glume with the nerves strongly hispid above the 



middle. 3. S. sanguinale. 



Spikelets 3 mm. long or more; third glume with the nerves smooth or nearly so. 



4. S. marginatum. 



1. S. Ischaemum (Schreb.) Nash. Stems 2-5 dm. long, at last prostrate 

 and rooting; leaf-blades 1.5-13 cm. long, 2.5-6 mm. wide, smooth and glabrous 

 on both sides; racemes 2-5, 2-8 cm. long; spikelets fully 2 mm. long, elliptic, 

 acute; first glimie rudimentarj' or wanting. Panicum lineare Krock., not L. 

 P. glabrum Gaud. Syntherisma humifusum (Pers.) Rydb. Waste places, fields, 

 and roadsides: N.S. — Fla. — Colo. — Mont.; introduced from Eu. Plain — Mont. 

 Jl-S. 



2. S. paniceum (Sw.) Nash. Stem tufted, 1-4.5 dm. high, glabrous; sheaths 

 glabrous; blades glabrous, up to 1 dm. long, 6 mm. wide; racemes 3-5, digitate, 

 up to 1 dm. long; rachis winged; spikelets about 1.3 mm. long, white, acute, el- 

 liptic; first glume wanting, second and third subequal, nearly equalling the 

 lemma, appressed-pubescent, 3-5-nerved. Waste places: n Mex. — Colo. — ■ 

 W. Ind.; also in the Old World. Son. 



3. S. sanguinale (L.) Diilac. Stem 3-10 dm. high, prostrate at the base and 

 rooting; leaf-blades 4-20 cm. long, 4-10 mm. wide, more or less papillose-hirsute 



