GRASS FAMILY 51 



than the second. Lemma 3-nerved, the nerves densely pilose with long silky- 

 hairs; midnerve usually excurrent into a short awn. Palet as long as the lemma, 

 2-nerveil, densely pilose between the nerves. Stamens 3. Styles distinct; 

 stigmas plumose. 



1. B. tricholepis (Torr.) Nash. Stem often jMirplish, glabrous, 3-10 dm. 

 high; leaf-blades invohite, 5-15 cm. long; panicle oblong, open, 1-1.5 dm. long; 

 spikelets 2.5-3 nun. long; empty glumes oblong, obtuse, nearly equal. Spor- 

 obolus tricholepis Torr. Mountain valleys: Tex. — Colo. — Utah — Ariz.; Mex. 

 Submont. — Subalp. Jl-N. 



27. SPOROBOLUS R. Br. Drop-seed, Rush-grass. 



Perennials or rarely annuals. Inflorescence a panicle, either open or narrow 

 and spike-like. Spikelets usually 1-flowered; flowers perfect. Empty glumes 2, 

 the first shorter than the second. Lemma usually longer than the second glume. 

 Palet 2-nerved, often deeply 2-cleft, about equalling the lemma. Stamens 2 or 

 3. Styles short, distinct; stigmas plumose. Grain free from the lemma and 

 readily dropping off. 



Perennials. 



First glume one-half as long as the second or less; plants not with long, scaly root- 

 stocks. 

 Branches of the panicle verticillate. 1. S. argutus. 



Branches of the panicle scattered. 



Spikelets about 2 mm. long; first glume lanceolate. 



Sheath naked or sparingly ciliate at the throat; empty glumes glabrous. 

 Plant 3 dm. liigh or less; spikelets long-pedicelled ; sheaths sparingly 



villous. 9. S. tcxanus. 



Plant 5-10 dm. high; spikelets short-pedicelled ; sheaths glabrous. 



2. S. airoides. 

 Sheath with a conspicuous tuft of hairs at the throat; empty glumes scab- 

 rous on the keel. 

 Leaf-blades widely spreading, involute; sheath pubescent with long 



hairs, at least towards the base. .3. S. Ncalletji. 



Leaf-blades not widely spreading; sheaths glabrous, except the apex, 

 and slightly on the margins. 

 Panicle narrow and spike-like. 4. S. strictus. 



Panicle not spike-like. 



Panicle always exserted, oblong, comparatively narrow; its 

 lower branches but little, if anj', e.xceeding the upper ones. 



5. S. flexuosus. 

 Panicle usually more or less included in the sheath; its lower 

 branches much exceeding the upper ones. 6. S. cryptandrus. 

 Spikelets 4.5-5 mm. long; first glume subulate, usually awned. 



7. S. helerolepis. 

 First glume almost equalling the second; plants with long, scaly rootstocks. 



8. S. asperifolius. 

 Annuals; empty glumes almost equal, ovate. 10. S. confusus. 



1 S. argutus (Nees) Kunth. Tufted perennial; stem 1-4 dm. high, erect or 

 decumbent at the base; leaf-blades 2.5-5 cm. long, 2-4 mm. wide, often sparingly 

 hairy at the base; panicle-branches 1-2.5 cm. long; .spikelets 1.5 mm. long. 

 Plains: Tex. — -Ivans. — Colo. — Mex.; W. Ind., C. Am. and S. Am. Son. Ap.-O.; 

 in the tropics the year around. 



2. S. airoides Torr. Densely tufted perennial; stem 5-10 dm. high, erect; 

 leaf-blades sometimes sparingly hairy at the base, 1-3 mm. wide, involute, 

 5-35 cm. long; panicle 1-4 dm. long, its branches at length widely spreading; 

 spikelets 1.5-2 mm. long; glumes acute, glabrous. Dry plains and river valleys: 

 Tex. — Mo. — -Mont. — -Calif. Plain — ■Submont. Au-S. 



3. S. Nealleyi Vasey. Tufted perennial; stems 3-4 dm. high, rigid; leaf-blades 

 2.5-3.5 cm. long, rigid, light-green, spreading, involute; panicle open, branches 

 ascending; spikelets 1.5 mm. long; lower empty glume lance-subulate; second 

 glume and the lemma lanceolate and acute. Dry ground: Tex. — Colo. Son. 

 Jl-S. 



4. S. strictus (Scribn.) Merr. Tufted perennial; stem strict, 5-10 dm. high, 

 glabrous; blades 5-20 cm. long, 3-5 mm. broad, mostly flat, glabrous; panicle 

 1-2 dm. long, the base included in the upper sheaths; flowers pale or green, 

 shining; empty glumes lanceolate, 2-2.5 mm. long, acute, smooth. River bot- 

 toms: Tex. — Utah — -Ariz. Son. Je-0. 



