GRASS FAMILY 33 



1. S. scoparium (Michx.) Xash. Perennial with a strong rootstock; stems 

 tufted. 4-15 dm. high, glabrous, scabrous, and in the western form usualh- glau- 

 cous: leaf-blades 4-6 cm. long, 8 mm. wide or less, scabrous and sometimes 

 hirsute at the base; racemes 3-6 cm. long, with white-hairy internodes and pedi- 

 cels; sessile spikelet 5-7 mm. long; awn of the lemma geniculate, 8-15 mm. long, 

 twisted at the base; pedicellate spikelet 2-4.5 mm. long, tipped with an awn 1 

 mm. long or less. Ajulropogon scoparius Michx. Drv sandy soil: N.B. — Fla. — 

 Tex.— N.M.— Alta. Plain— Suhivont. Jl-S. 



2. AMPHILOPHIS Nash. Beard-grass. 



Perennial grasses, resembling Audropogon, with showy, often silvery panicles. 

 Racemes numerous, the internodes with manifestly thickened margins; the 

 median portion thin and translucent. Sessile spikelet of 4 glumes, the outer 2 

 indurate, the first 2-keeled, the second 1-keeled, the third and the lemma hya- 

 line, the latter very narrow, gradually merging into the awn; the pedicellate 

 spikelet staminate and similar, or sterile and reduced. Stigmas plumose. 



1. A. saccharoides (Sw.) Nash. Tufted perennial, smooth and glaucous; 

 stems 5-10 dm. high, simple or somewhat branched; leaf-blades 1-5 dm. long, 

 3-7 mm. wide, rough above; racemes 1-4 cm. long, the terminal hairs 1^-2 

 times as long as the internodes; sessile spikelet 4 mm. long, half longer than the 

 internodes; awn geniculate, more or less twisted, 1-1.5 cm. long; pedicellate 

 spikelet consisting of a single glume 2-3 mm. long. Andropogon glaucum Torr. 

 A. Torreijanum Steud. Drv soil: Tex.^Mo. — Colo.^Ariz.; Mex. .So«. .Je- 

 Au. 



3. ANDROPOGON (Royen) L. Bluestem, Beard-grass. 



Perennial grasses, tufted or from elongated rootstocks, with spike-like racemes, 

 disposed in pairs or sometimes in 3's or more, terminating the stem or its branches. 

 Spikelets sometimes with a ring of short hairs at the base, in pairs at each node 

 of the articulated and frequently hairy rachis, one sessile, the other pedicellate. 

 Sessile spikelet of 4 scales, the outer 2 indurated, often pubescent, the third 

 usually hyaline, the lemma entire or 2-toothed at the apex, bearing a straight 

 contorted or spiral awn, or sometimes awnless; palet small, hyahne. Pedicellate 

 spikelet usually sterile, of 1 or 2 glumes, sometimes of four glumes and enclosing 

 a staminate or more rarely a perfect flower, or frequently entirely wanting, the 

 first glume rarely short-awned. Stamens 1-3. Styles distinct; stigmas plumose. 



Lemma of the sessile spikelets with a long geniculate awn, more or less spiral at the base. 

 Outer two glumes of the sessile spikelets more or less hispidulous all over; hairs of the 

 rachis-internodes usually 2 mm. long or less, mostly white. 1. A. prorincialis. 



Outer two glumes of the sessile spikelets smooth or nearly so, except on the nerves; 

 hairs of the rachis-internodes 3-4 mm. long, usually yellow. 2. A. chrysncomus. 

 Lemma of the sessile spikelets awnless or with a short straight untwisted awn. 

 Marginal hairs of the pedicels and rachis-internodes copious, stiff. 3. .4. HalUi. 

 Marginal hairs of the pedicels and rachis-internodes scant, lax, crisp, or almost 

 wanting. 4. A. paucipilus. 



1. A. provincialis Lam. Stem 1-2 m. high; sheaths glabrous, or sometimes 

 slightly hairy; leaf-blades 1.5-6 dm. long, 5-12 mm. wide, usually glabrous and 

 smooth beneath, slightly scabrous above and somewhat hairy at the base; racemes 

 in 2's-6's, 5-10 cm. long; sessile spikelet 7-10 mm. long; av\-n 7-15 mm. long; 

 pedicellate spikelet nearly as large, staminate, awnless. A. furcatus Muhl. 

 Meadows: Me.— Fla.— Tex.— N.IVl.— Mont.— Sask. Plain-Submont. Jl-S. 



2. A. chrysocomus Nash. Stem 7-15 dm. high; sheaths smooth and 

 -glabrous; leaf-blades 2-3 dm. long, 7 mm. wide or less, smooth beneath, slightly 



scabrous above; racemes in 2's-4's, 5-9 cm. long, long-exserted; sessile spikelet 

 about 1 cm. long; outer two glumes hispid on the nerves; awn 10-12 mm. long; 

 pedicellate spikelet awnless. Prairies and plains: Neb. — -Tex. — -Colo. Plain — 

 Submont. Jl-S. 



3. A. Hallii Hack. Stem robust, 1-2 m. high, more or less glaucous, 

 glabrous; sheaths glabrous and glaucous; leaf-blades 2-3 dm. long, 5-8 mm. wide; 

 spikes in 2's-5's, 5-10 cm. long; hairs of the internodes about 2 mm. long, yellow- 

 ish or whitish; sessile spikelet about 8 mm. long; outer glumes glabrous at the 



