GRASS FAMILY 47 



Stem 1-3 dm. high, almost naked above; panicle 3-7 cm. long; awn 1-4 mm. long. 

 Spikelets 3—1 mm. long; awn 2-4 mm.; leaf-blades usually stiff. 



18. M. subalpina. 

 Spikelets about 2 mm. long; awn 1-2 mm.; leaf-blades filiform. 



19. M. filiculmis. 

 Panicle open, its branches long and spreading. 



Plants densely cespitose, branched onlj at the base. 



Secondary branches of the panicle single: basal leaves short, strongly recurved. 



20. A/, gracillima. 

 Secondary branches of the panicle fascicled; basal leaves not recurved. 



21. M. pungens. 

 Plants diffusely branched, prostrate. 22. M. Porteri. 



1. M. mexicana (L.) Trin. Perennial; stem decumbent, prostrate, or erect, 

 smooth, braucliL'il and very leafy; leaf-blades scabrous, 4-15 cm. long, 2-6 

 mm. wide; panicle o-lo cm. long; spikelets 2.5-3 mm. long; empty glumes some- 

 what unequal, scabrous on the keel. Wet meadows and swamps: N.B. — N.C. — 

 Te.\. — Colo. — Wyo. — N.D. Plain — Subuiont. Je-S. 



2. M. racemosa (Michx.) B.S.P. Perennial; stem erect, 3-10 dm. high, 

 branched, smooth; leaf-blades 5-12 cm. long, 2-6 mm. wide, scabrous; panicle 

 3-10 cm. long, dense, usually interrupted; branches 1-2.5 cm. long, erect; spike- 

 lets much crowded; lemma one-half to two-thirds as long as the empty glumes, 

 acuminate to awn-pointed. M. glomerata Torr. Wet places: Newf. — N.J. — 

 Mo.— X.M.— Utah— B.C. Plain— Mont. Jl-S. 



3. M. comata (Thm-b.) Benth. Perennial; stem 3-7 dm. high, erect, smooth; 

 leaf-blades 5-12 cm. long, erect, flat, scabrous; panicle often tinged with purple, 

 5-10 cm. long, dense, 1-1.5 cm. thick; empty glumes equal or the second a little 

 longer, 2.5-3 mm. long; lemma a little shorter; awn 6-10 mm. long. Prairies 

 and river valleys: Mont. — Colo. — Calif. — -Wash. Subniont. — Mont. Jl-S. 



4. M. Wrightii Vasey. Somewhat tufted perennial, with short rootstock; 

 stem erect or decumbent at the base, 3-7 dm. high, somewhat compressed; leaf- 

 blades 6-15 cm. long, scabrous above, about 2 mm. wide; panicle cylindric, more 

 or less interrupted; outer glumes nearly equal, 2 mm. long, thin, ovate or lanceo- 

 late, awn-pointed; lemma a little longer, tipped with a short awn. Mountains: 

 X.M. — Colo. — Ariz.; Mex. Submont. Jl-S. 



5. M. cuspidata (Terr.) Rydb. Somewhat tufted perennial, occasionally 

 with elongated scaly rootstocks; stem slender, 3-6 dm. high, glabrous; leaf- 

 blades 2.5-10 cm. long, less than 2 mm. wide, involute-setaceous at least when 

 dry; panicle 4-12 cm. long; emjjty glumes about 2 mm. long, scabrous on the 

 keel; flowering glume long-acuminate, about 3 mm. long. Sporobolus brevif alius 

 (Xutt.) Scribn. Dry soil: ^lan. — ]\Io. — Colo. — Alta. Plain — Submont. Jl-S. 



6. M. Thurberi (Scribn.) Rydb. Tufted perennial with a scaly rcotstock; 

 stems 1.5-3 dm. high; leaf-blades 1-3 cm. long, strongly involute, the lower 

 more or less spreading; panicle 2-5 cm. long, 2-3 mm. thick; empt}^ glumes 

 equal, 1-nerved, lanceolate, 3 mm. long, usually purplish; lemma lanceolate, 

 cuspidate, 3-nerved, 4-4.5 mm. long. Sporobolus filiculmis Vasey, not Dewey. 

 S. Thurberi Scribn. Dry places and canons: Tex. — Colo. — N.M. Son. — Sub- 

 mont. Jl-S. 



7. M. squarrosa (Trin.) Rydb. Tufted perennial; stems less than 1 dm. 

 high, decumbent at the base, glabrous and almost smooth; leaf -blades scarcely 

 1 cm. long; panicle 1-2 cm. long, narrow and rather few-flowered; empty glumes 

 1-1.5 mm. long, 1-nerved, straw-colored; lemma lanceolate, acute, 1.5-2 mm. 

 long. Sporobolus depaupcratus (Torr.) Scribn. Dry, sandy or alkali soil: Wash. 

 — Mont. — Wyo. — ^Calif. Son. — Submont. Jl-Au. 



8. M. Schreberi Gmel. Perennial, with a creeping, scaly rootstock; stem 

 3-9 dm. long; leaf -blades 3-9 cm. long, scabrous; panicle 5-20 cm. long, 2-5 

 mm. thick, lax; empty glumes small, the first often wanting; lemma without the 

 awn about 2 mm. long, strongly scabrous; awn 1-4 mm. long. M. diffusa Willd. 

 Dry hills and woods: Me. — Fla. — Tex. — w Neb. — Minn. Boreal — Plain. Au-S. 



9. M. Richardsonis (Trin.) Rydb. More or less tufted perennial, with a 

 strong rootstock; stem 1-4.5 dm. high, erect or decumbent at the base, slender, 

 smooth; leaves 1-5 cm. long, usually involute; panicle 1-7 cm. long, 2-4 mm. 



