68 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM, 
26. MUHLENBERGIA Schreb. 
Perennials or rarely annuals, with small spikelets; culms simple or much branched; 
leaves long or short, flat or involute; panicles narrow and spikelike or open and widely 
spreading; spikelets 1-flowered; rachilla jointed above the glumes, forming a very short 
and usually hairy callus below the lemma but not extending beyond it; glumes 
membranaceous or hyaline, 1 to 3-nerved or nerveless, usually unequal and shorter 
than the lemma, acute or mucronate; lemma narrow, smooth, or more or less pilose 
below, 3 or 5-nerved, awned from the acute apex or from between the teethof the 
bidentate apex; awn straight or flexuous; palea thin, 2-nerved; stamens 3; grain 
closely enveloped by the lemma, 
KEY TO THE SPECIES. 
Plants tall, | meter high or more, stout; panicle 25 to 35cm. long. 
Plants lower, less than 1 meter high, mostly less than 60 cm., 
more slender; panicles shorter, less than 25 cm. long. 
Panicles open and spreading. 
Plants diffusely branched throughout, weakly ascend- 
ing or decumbent ......--........-22------24-- 
Plants erect, branched only at the base. 
Secondary branches of the panicle clustered; leaves 
stiff and spiny-pointed....................-- 
Secondary branches of the panicle single; leaves 
neither stiff nor spiny-pointed. 
Basal leaves 5 cm. long or less, strongly re- 
curved.......2-..-2 2202 eee ee ee eee eee 
Basal leaves more than 5 cm. long, not recurved. 
Awns short, 4mm. Jong; leaf blades 5 to 10 
cm. long; panicles green............ 
Awns long, 10 to 15 mm.; leaf blades 
about 20 cm. long; panicles dark 
purple............-222--2222--2---- 
Panicles narrow and spikelike. 
Annual, 5 to 15 cm. high...................0......22-- 
Perennials, mostly more than 15 cm, high. 
Glumes subulate; plants with leafy branches and 
long scaly rhizomes. 
Glumes about as long as the lemma, not awned . 
Glumes longer than the lemma, awned. 
Lemmas only slightly villous........... 
Glumes lanceolate to ovate; plants various. 
Lemmas awnless or with very short awns. 
Glumes under half as long as the lemmas. . 11. 
Glumes more than half as long as the 
lemmas. 
Glumes acute, not awned. 
Panicles on long peduncles. ....... . 
Panicles partly included in the 
sheaths.........-.2-.---------- 
Glumes awned. 
Lemmas hairy below........-..... 
5. 
8. 
16. 
16. 
M. emersleyi. 
M. portert. 
. M. pungens. 
M. gracillima. 
M. arenicola. 
M. rigida. 
. M. schaffneri. 
M. mexicana. 
. M. racemosa. 
Lemmas covered with long white hairs.... 10. 
M. comata. 
M. squarrosa. 
M. thurberi. 
M. repens. 
M. lemmoni. 
