288 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
Spikelets 3 mm. long; spikelets clus- 
tered toward the ends of the 
stifly ascending branches; 
blades flat, about 2 mm.wide .. 22 
Spikelets about 1.5 mm. long, not clus- 
tered; blades filiform, about 0.5 
mm. wide, often involute...... 19 
Plants not producing creeping rhizomes. 
.Glumes less than 1 mm. long. 
Panicle spreading. ....-.-.-2.2....2.202220-2-2 eee 23 
Panicle narrow. 
Ligule very short; blades flat or becoming involute.... 24 
. M. plumbea. 
. M. breviseta. 
. M. seatoni. 
. M. spiciformis. 
Ligule 2 to 3 mm. long; blades closely involute........ 25. M. parviglumis. 
Glumes more than 1 mm, long. 
Culms lax, clambering, decumbent and rooting at base; 
blades flat, short, as much as8 mm. wide.......... 26 
Culms not lax, erect at base, but sometimes becoming 
decumbent. 
Plants widely spreading, much branched, wiry; pan- 
icles diffuse. ...........222000000222022000000. 27 
Plants not widely much branched. 
Culms ascending, more or less decumbent below, 
rather slender; blades short. 
Awn of lemma long and slender; spikelets short- 
pediceled on the main panicle branches...... 28 
Awn of lemma shorter than its body; spikelets 
slender-pediceled in an open panicle........ 29 
Culms erect or nearly so. 
Second glume 3-toothed. 
Teeth awned; lemma hirsute................. 30 
Teeth unawned;lemmaslightly pubescent. ... 31 
Second glume entire or sometimes erose or 2- 
toothed. 
Awn of lemma not longer than the body. 
Panicle close, spike-like; glumes awned...... 33 
Panicle narrow or open, not spike-like. 
Blades mostly less than 10 cm. long; pani- 
icle open, the slender branches as- 
cending..........--2..-.-2.20..00202. 32 
Blades more than 10 cm. long; panicle nar- 
row, the branches appressed. 
Glumes 3 to 4 mm. long; panicle lead- 
colored; branches rather stout. ..... 34. 
Glumes | to 2 mm. long; branches capil- 
lary. 
Panicle branches naked below; panicle 
purple...............0.0.000..... 35 
Panicle branches with short spikelet- 
bearing branchlets at base........ 56 
Awn of lemma longer than the body. 
Awns yellow, flexuous; plants 20 to 30 cm. 
high. 
Glumes subequal. ............. veeeeeeas 36. 
Glumes unequal, the first shorter.......... 37. 
. M. setarioides. 
. M. porteri. 
. M. brevifolia. 
. M. artzonica. 
. XM. gracilis. 
. M. quadridentata. 
_ M. wrightii. 
. M. arenicola, 
M. firma. 
. M. laxiflora. 
. M. acuminata. 
M. scabra. 
M. flaviseta, 
