358 MISC. PUBLICATION 200, U. S. DEPT. OF AGRICULTURE 



mesas and rocky hills of the Western States, M. pauciflora, M. 

 enter sleyi, and M. wrightii in the Southwest. 



la. Plants annual (see also M. uniflora). 



Glumes pilose ; spikelets on slender pedicels 1. M. texana. 



Glumes glabrous; spikelets on short thick pedicels. 



Panicles narrow but loose; awn 1 to 3 cm long 2. M. microsperma. 



Panicles more or less spikelike; awn reduced to a mucronate point, sometimes 

 as much as 1 mm long. 



Lemma about 4 mm long 3. M. depattperata. 



Lemma about 2 mm long 4. M. filiformis. 



lb. Plant perennial. 



2a. Creeping rhizomes present or the slender decumbent base rooting at the 

 nodes (rhizomes short in M. dumosa and M. calif ornica) . 

 3a. Rhizomes wanting; base of slender branching culms decumbent and 

 rooting at nodes. 



Spikelets awnless 15. M. uniflora. 



Spikelets awned. 



Glumes minute, the first often obsolete 30. /M. schreberi. 



Glumes evident (see also M. schreberi var. palustris). V___^ 



31. M. CURTISETOSA. 



3b. Rhizomes usually prominent, scaly, creeping. 

 4a. Panicles open, the spikelets on slender pedicels. 



Spikelets awned, 4 to 5 mm long; blades involute- _ 16. M. pungens. 

 Spikelets awnless, acutish or mucronate, 1 to 2 mm long; blades flat. 



Panicle oblong; eastern species 14. M. torreyana. 



Panicle as broad as long; western species. 



Ligule 1 to 2 mm long, auricled 12. M. arenacea. 



Ligule minute, not auricled 13. M. asperifolia. 



4b. Panicles narrow, more or less condensed, the spikelets on short 

 pedicels. 

 5a. Hairs at base of floret copious, as long as the body of the lemma. 



32. M. ANDINA. 

 5b. Hairs at base of floret inconspicuous, not more than half as long as 

 the lemma. 

 6a. Blades 2 mm wide or less, mostly short and involute, 



Culms tall, stout, somewhat woody at base, as much as 6 mm thick, 



1 to 3 m tall 19. M. dumosa. 



Culms lower, slender. 



Blades mostly 5 to 10 cm, rarely 15 cm long. 20. M. glauca. 

 Blades mostly less than 5 cm long. 



Culms widely creeping, the blades fine, conspicuously recurved- 

 spreading. Culms smooth. Ligule less than 1 mm long. 



Spikelets about 3 mm long 5. M. repens. 



Spikelets about 2 mm long 6. M. utilis. 



Culms erect or decumbent at base, not widely creeping (some- 

 times spreading in M. squarrosa) . 

 Glumes ovate, about half as long as the floret; ligule 2 to 3 

 mm long. Culm nodulose-roughened. 



7. M. SQUARROSA. 



Glumes a little shorter than the floret; ligule minute. 

 Plants forming dense cushions; sheaths glabrous; leaves 

 crowded toward the base, the blades involute; lemma 



mucronate to short awned 8. M. thurberi. 



Plants forming loose bunches; sheaths pubescent; leaves 

 not crowded, the blades flat; lemma with an awn 1 



to 3 mm long 9. M. curtifolia. 



6b. Blades flat, at least some of them more than 3 mm wide. 



7a. Panicles loosely flowered, slender, much exceeding the leaves 



(see also M. sylvatica); glumes broad below, abruptly pointed, 



shorter than the body of the lemma. 



Culms slender, rather weak, becoming much branched, glabrous 



or slightly scabrous below the nodes. Lemma acuminate, 



2.5 to 3.5 mm long, awned 24. M. brachyphylla. 



Culms erect, simple or sparingly branched. 



Spikelets 1.5 to 2.5 mm long; lemma awnless or awn-tipped; 

 blades commonly not more than 5 to 7 mm wide. 



22. M. SOBOLIFERA. 



