Panicle contracted, narrow, often slender, its branches erect or appressed.

Outer scales 1/4 as long as the flowering scale or less.

First scale minute, often wanting; flowering scale with an awn twice its length or less.

1.

M. Schreberi.

First scale about 2/3 as long as the second; flowering scale with an awn 3-4 times its length.

2.

M. palustris.

Outer scales more than 1/4 as long as the flowering scale.

Plants with numerous and conspicuous rootstocks covered with short appressed scales.

Flowering scale awnless, or sometimes awn-pointed.

Outer scales ovate to broadly lanceolate, cuspidate, about 1/2 as long as the flowering

scale.

3.

M. sobolijera.

Outer scales subulate, equalling or exceeding the flowering scale, awn-pointed or awned.

Outer scales about equal in length to the flowering scale, about 1 1/2" long, sharp-

pointed.

4.

M. mexicana.

Outer scales exceeding the flowering scale, generally twice its length, about 2 1/2"

long, awned.

5.

M. racemosa.

Flowering scales long-awned, the awn usually twice as long as the scale, sometimes shorter.

Outer scales 1/2-2/3 as long as the flowering scale, ovate to broadly lanceolate, cuspidate.

6.

M. tenuifiora.

Outer scales equalling the flowering scale, subulate.

Basal hairs not more than 1/2 as long as the flowering scale.

Spikelets consisting of 3 scales and 1 perfect flower.

7. M. umbrosa.

Spikelets consisting of 4 scales, the third with a perfect flower, the fourth

empty and awned.

8.

M. ambigua.

Basal hairs as long as the flowering scale.

9.

M. comata.

Plants without rootstocks, or these rarely present and with few scattered long scales.

Annual; outer scales less than 1/2 as long as the spikelet, rounded or truncate at the

erose apex.

10.

M. simplex.

Perennial; outer scales 1/2. as long as the spikelet or more, acute or acuminate.

Culms simple at the base, finally much-branched above; ligule about 1" long, acutish;

outer scales about 1/2 as long as the spikelet, acute.

11.

M. brevifolia.

Culms branched at the very base only, simple above; ligule 1/4" long or less, erose-truncate; outer scales more than 1/2 as long as the flowering scale, attenuate.

12.

M. cuspidata.

Panicle open, its branches long and spreading, slender.

Culms 16' tall or less, from much-branched rootstocks; blades 2' long or less.

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

13.

M. gracillima.

Secondary branches of the panicle fasciculate; basal leaves few, not recurved.

14.

M. pun gens.

Culms 20' tall or more; rootstocks none; blades elongated.

15.

M. capillaris.