34 POACEAE 



base, pubescent towards the apex; awn straight, 4-10 mm. long or sometimes 

 wanting; pedicellate spikelet awnless, usually larger than the sessile one, stam- 

 inate. Sandy soil: N.D. Miss. Mex. Mont. Plain Son. Jl-S. 



4. A. paucipilus Nash. Stem 1-1.5 m. tall, stout; sheaths smooth and 

 glabrous; leaf -blades 3 dm. long or less; racemes in 2's-3's, 5-7 cm. long, exserted; 

 sessile spikelets 9-10 mm. long; outer 2 glumes hispid on the nerves toward the 

 apex, pubescent towards the summit; awn almost none; pedicellate spikelet 

 similar to the sessile one, staminate. Dry soil: Mont. Neb. Plain. Jl. 



4. SORGHASTRUM Nash. INDIAN GRASS. 



Perennials with rootstocks. Panicles large, with the principal branches soli- 

 tary but branching near the base and hence appearing verticillate. Sessile 

 spikelet dorsally compressed; empty glumes 3, the outer two indurate, often 

 hairy, the third hyaline. Lemma hyaline, with a long awn, which is spiral at 

 the base. Pedicellate spikelet wanting or rudimentary, usually represented 

 merely by a hairy pedicel at one side of the sessile spikelet, or at the ends of the 

 branches by two pedicels, one on each side. Styles distinct; stigmas plumose. 



1. S. nutans (L.) Nash. Perennial, with a scaly rootstock; stems 1-2.5 m. 

 high; leaf-sheaths usually smooth and glabrous; blades 3-6 dm. long, 5-13 mm. 

 wide, very rough; panicles 2-5 dm. long, loose, the apex usually nodding; spike- 

 lets 6-8 mm. long, lanceolate, the 2 outer glumes golden-brown, the first one 

 densely pubescent with long erect hairs; awn geniculate, 1-1.5 cm. long, closely 

 spiral up to the bend, then loosely twisted. Andropogon nutans L. Chrysopogon 

 nutans A. Gray. Meadows: Out. Fla. Tex. Ariz. Sask.; n Mex. Plain 

 Submont Son. Jl-S. 



5. HOLCUS L JOHNSON GRASS, BROOM CORN, SUGAR CORN. 



Perennials with rootstocks, or annuals. Branches of the large panicle verti- 

 cillate. Spikelets in pairs or at the ends of the branches in 3's, 1 sessile and 

 pistillate, 1 or 2 pedicelled and staminate or neutral. Empty glumes 3, the 

 outer two indurate, the third hyaline. Lemma hyaline, awned, or awnless. 

 Styles distinct; stigmas plumose. [Sorghum Pers.] 



1. H. halapense L. Perennial; stem 5-15 dm. tall; leaf-blades 2-5 dm. 

 long, 0.5-3 cm. wide; panicle 1.5-5 dm. long, oblong to oval; sessile spikelet 4.5- 

 5.5 mm. long, ovoid, the two outer glumes densely appressed-pubescent; awn 

 readily deciduous, 1-1.5 cm. long; pedicellate spikelets 5-7 mm. long, lanceolate, 

 the 2 outer glumes sparingly pubescent. Sorghum halapense Pers. JOHNSON 

 GRASS. In fields and waste places: Pa. Fla. Tex. Colo.; Calif.; Mex., 

 C. Am. and S. Am.; escaped from cultivation. Je-D. 



6. PLEURAPHIS Torr. BLACK BUNCH-GRASS, GALLETA GRASS, 



TOBOSA GRASS. 



Tufted perennials with scaly rootstocks. Spikelets in sessile clusters of three, 

 forming a spike-like inflorescence; central spikelet 1-flowered, the lateral ones of 

 2 staminate flowers. Glumes 3 in the central flower, the outer two-ridged, the 

 first larger, 2-toothed at the apex, awnless or with an awn between the teeth, 

 the second narrower and keeled, the third thin-membranous and like the lemma. 

 Glumes of the lateral flowers only two. Styles a little united at the base; stig- 

 mas short-plumose. 



Stem and leaf-sheath, at least the lower ones, densely woolly. 1. P. rigida. 



Stem and leaf-sheath not woolly. 



Outer glumes of the spikelets cuneate, awnless; nerves strongly divergent. 



2. P. mutica. 



Outer glumes linear or oblong, awned; nerves parallel. 3. P. Jamesii. 



1. P. rigida Thurb. Stem 3-8 dm. high, branching, covered with a dense 

 tomentum; leaf-blades 3-12 cm. long, rigid, 3-5 mm. wide, often involute; spike 

 3-10 cm. long; glumes of the central perfect spikelet cuneate at base, bifid above, 

 fringed with wool; awn divergent, a little exceeding the glume; glumes of the 

 lateral spikelets irregularly toothed above; awns short, straight or recurved. 

 Hilaria rigida Benth. Desert regions : s Utah 'Ariz. s Calif. L.Calif. L. Son. 

 Ap-Je. 



