46 POACEAE 



and convolute, densely pubescent with silky hairs, with an obtuse callus at the 

 base, and a deciduous straijiht awn at the apex. Styles distinct; stigmas plumose. 

 Grain oblong, free, enclosed in the lemma. 



1. E. hymenoides (R. & S.) Rydb. Stem 3-6 dm. high, erect, rigid, smooth; 

 leaf-blades 1.5-3 dm. long, involute, less than 2 mm. wide; panicle 1.5-3 dm. 

 long; branches spreading, flexuose; lower glumes 6-S mm. long, long-acuminate, 

 with somewhat spreading tips; lemma 4 mm. long, broadly ellipsoid, densely 

 pube.scent with white hairs. Eriocoma cuspidata Xutt. Bad lands and sandy 

 places: Sask. — Kans. — Tex. — Calif. — Wash.; Mex. Plain — Mont. IMj'-Jl. 



21. MUHLENBERGIA Schreb. 



Perennials or annuals. Inflorescence a narrow contracted or open diffuse 

 panicle. Spikelets 1-flowered; flower perfect. Empty glumes 2, membranous 

 or hyaline, persistent, keeled, acute to short-a^Tied, the second sometimes 3- 

 toothed. Lemma somewhat rigid, enclosing the palet, entire or 2-toothed at the 

 apex, obtuse, acute, or awned. Stamens usually 3. Styles distinct; stigmas 

 plumose. 



Panicle contracted, narrow, spike-like, the short branches rarely spreading. 



Empty glumes awl-shaped: leafy and branched plants, with long rootstocks covered 

 by imbricated scales. 

 Lemma not awned; basal hairs not equalling the lemma. 



Empty glumes about equalling the lemma in length, sharp-pointed, about 3 



mm. long. 1. M. mexicana. 



Empty glumes exceeding the lemma, generally twice as long, awned, about 

 .5 mm. long. 2. JV/. racemosa. 



Lemma distinctly a^\Tied: basal hairs equalling the lemma. 3. A/, comata. 

 Empty glumes lanceolate to ovate. 



Second glume not toothed or slightly so. 



Lemma a^vnless oi rarely very short-awned. 



Empty glumes more than half as long as the lemma. 



Plant 1.5-7 dm. high; sheaths close; empty glumes acuminate, lance- 

 olate. 

 Lemma scabrous, green or dark. 



Panicle dense, obtuse, 5-10 mm. wide. 4. M. Wrightii. 



Panicle slender and lax, attenuate at the apex, less than 5 mm. 

 wide. 5. M. cuspidata. 



Lemma more or less purplish, sparingly long-hairy. 



6. J\/. Thurberi. 

 Plant less than 1.2 dm. liigh; sheaths loose: lower leaves lanceolate, 

 short, squarrose; empty glumes ovate, acute. 7. A/, squarrosa. 

 Empty glumes less than half as long as the lemma, obtuse or abruptly 

 acute. 

 Spikelets (excluding the awn if present) 1.5 mm. or more long. 

 Plant with a strong perennial, scaly rootstock. 



Empt\ glumes less than one-fom-th as long as the lemma; stem 

 diffuse, decumbent or creeping; plant not tufted. 



8. M. Schrcbcri. 

 Empty glumes one-third as long as the lemma or longer; stem 



erect or decumbent at the base only; plant tufted. 



9. M. Richardsonis. 

 Plant annual; rootstock, if any, very slender. 



Lemma merelj awn-pointed, decidedly purplish; plant 1-2 dm. 

 high. 

 Spikelets 2 mm. long or more; inflorescence short and rather 



dense; stem 0.5-1 mm. thick. 10. M. simplex. 



Spikelets about 1.5 nun. long: inflorescence slender and lax; 

 stem very slsnder, filiform. 11. M. filiformis. 



Lemma with a distinct avra 0.5-1 mm. long, greenish; plant 

 4-6 cm. high. 12. M. aristata. 



Spikelets about 1 mm. long; plant less than 4 cm. liigh, annual. 



13. yr. Wol/ii. 

 Lemma long-awned. 



Leaf-blrdes erect, glabrous or minutely scabrous; stem and sheaths glab- 

 rous. 

 Lemma glabrous; rootstock short and woody. 14. M. pauciflora. 



Lemma pubescent on the lower half; rootstock slender, creeping, 

 branclied. 15. M. polycaulis. 



Leaf-blades spreading, as well at the stem below the nodes and the sheaths 

 scabrous-puberulent ; lemma pubescent on the lower half; rootstock 

 creeping. 16. M. curtifolia. 



Second glume sharply 3-5-toothed; flowering glume long-a-s\'Tied; awn at least 

 one-half as long as the glume. 

 Stem 3-6 dm. high, leafy; panicle 7-12 cm. long: awn 8-15 mm. long. 



17. M. gracilis. 



