523 | 
6. M. gracillima Torr. Culms 1 to }din. high, slender, usually naked and smooth 
below the panicle: leaves crowded at the base, 2 to 3 em, long, tiliform-involute, 
curved: culm leaves one or two: panicles about 1 din. long, usually purple; branches 
mostly single, naked below and with few subdivisions: spikelets about 3mm. long; 
empty glumes acute, the second one slightly larger, two-thirds as long as the floret; 
awn about equaling the floret.—Rocky canons, western Texas to Colorado and Ari- 
zona. 
* « Culms branched and somewhat spreading. 
+ Annual. 
7. M. Buckleyana Scribn. Culms 2 to 5 dm. high, spreading from the tufted 
base: leaves few near the base, mostly flat: panicle oblong, one-half to two-thirds 
as long as the culm, usually purple; branches subverticillate or single, sparsely sub- 
divided toward the extremities: spikelets 2 mm. long, on pedicels scarcely equaling 
themselves; empty glumes subequal, acute, ciliate, one-half as long as the slightly 
pubescent floret; floral glume rather broadly toothed at the apex; awn little shorter 
than the glume.—Gravelly bars and river banks, western Texas to Mexico, 
++ Perennial. 
8. M. Texana Thurb. Culms 3 to5dm. high, spreading, much branched through- 
out, somewhat hoary; leaves flat, not rigid, narrow, 3 to 8em, long: panicles about 
1 dm. long, terminating the numerous branches, usually vaginate at the base; 
branches mostly single, sparsely subdivided: spikelets 3to 4 mm. long, purple; 
empty glumes narrow, acute, three-fourths as long as the floret; glume and palet 
pubescent on the nerves; awn 4 to 6 mm. long.—High mesas, western Texas to Ari- 
zona, 
§ 2. Panicles narrow, contracted; pedicels short. —MUHLENBERGIA proper. 
* Culms branching. 
+ Leaves flat, 3 mm, wide: awn not more than twice as long as the spikelet: from scaly 
perennial rootstocks. 
9. M. diffusa Schreb. (NIMBLE WILL.) Culms 4 to 8 dm, high, diffusely branech- 
ing throughout: leaves thin, about 5 em, long: panicles numerous, 5 to 20 em, long, 
slender, interrupted ; branches single: spikelets 2 to 2.5 mm. long; first empty 
glume obsolete ; second minute, obtuse; floral glume seabrid; awn equaling or twice 
as long as the floret.—Dry hills and woods, northern Texas and northward. 
10. M. tenuiflora (Willd.) B.S. P. Culms 5 to 10dm. high, much branched above, 
leafy throughout: leaves thin, about 1 dim. long: panicles 6 to 20 cm. long, slender ; 
branches single, erect: spikelets subappressed, 3 to 4 mm. long; empty glumes sub- 
equal, acute, slightly seabrid on the prominent green keels, one-half to two-thirds 
as long as the floret; floral glume and palet somewhat pubescent near the base; 
awn3to 6mm. long. (Agrostis tenuiflora Willd., Muhlenbergia Willdenovit Trin. )\— 
Low, swampy land, northern Texas to Massachusetts and Minnesota. 
11. M. sobolifera (Muhl.) Trin. Culms 6 to 10 dm. high, branching above: leaves 
firm, ereet or spreading, 1 dim, long or less: panicle 6 to 15 cm. long, slender; branches 
single, erect: spikelets about 2 mm, long; empty glumes equal, two-thirds as long 
as the floret; floral glume pubescent near the base, mucronate or with an awn as 
long as itself. (Agrostis sobolifera Muhl,)—Sandy woodland, northern Texas and 
northward. 
— + Leaves very narrow, flat or involute; ligule short: in strongly rooted tufts or 
from scaly rootstocks. 
+ Awns not longer than the glomerate spikelets, 
