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



Old sheaths not flat and coiled. 

 Lemma pilose on lower part. 



Culms loosely tufted, hard and wiry at base; floret loosely 

 villous below. 



Glumes and floret about equal 36. M. polycaulis. 



Glumes about half as long as floret 37. M. arsenei. 



Culms closely or somewhat loosely tufted, slender but not hard 

 and wiry at base; floret densely pilose at base. 



38. M. MONTICOLA. 

 Lemma scaberulous, not pilose. 



Glumes less than 1 mm long. 39. M. parviglumis. 



_ Glumes about 2 mm long 40. M. pauciflora. 



9b. Panicle open, or at least loose, the branches naked at base (some- 

 times shortly so in M. metcalfei). 

 Plants widely spreading, much branched, wiry, the base knotty. 



41. M. PORTERI. 

 Plants erect, not widely spreading and much branched. 



Blades flat, short 18. M. arizonica. 



Blades elongate or, if short, involute. 

 Blades short in a basal cluster, involute. 



Panicle mostly less than 15 cm long; blades 1 to 3 cm long, 



curled or falcate 42. M. torreyi. 



Panicle mostly more than 20 cm long; blades commonly 5 to 8 



cm long 43. M. arenicola. 



Blades elongate, flat or involute. 



10a. Panicle usually not more than twice as long as wide at 

 maturity, the branches and pedicels stiff; awn of lemma less 

 than 5 mm long. 

 Plants with fibrous tuft at base; lemma awnless or with an 



awn as much as 2 mm long 49. M. expansa. 



Plants without fibrous tuft at base; lemma with an awn 2 to 



5 mm long 50. M. reverchoni. 



10b. Panicle elongate, at least 4 times as long as wide at maturity ; 

 awns of lemmas, or some of them, usually 10 mm long or 

 more. 

 Panicle relatively dense, the branches short; pedicels mostly 



shorter than the spikelets 47. M. metcalfei. 



Panicle loose, the capillary branches ascending to spreading. 

 Blades involute, subfiliform, scabrous; panicle pale or tawny. 



44. M. setifolia. 



Blades coarser, flat to involute; panicle purple (often tawny 



in M. emersleyi) . 



Panicle branches, or most of them, more than 10 cm long, 



the panicle diffuse at maturity __ 48. M. capillaris. 



Panicle branches not more than 10 cm long, the panicle 



not diffuse. 



Lower sheaths compressed-keeled; glumes as long as 



lemma or a little longer 54. M. emersleyi. 



Lower sheaths not compressed-keeled; glumes much 

 shorter than lemma 46. M. rigida. 



1. Muhlenbergia texana Buckl. (Fig. 732.) Annual; culms deli- 

 cate, erect or decumbent at base, 10 to 20 cm tall; blades mostly less 

 than 5 cm long, about 1 mm wide, scabrous; panicle oblong, more than 

 half the entire height of the plant, open, the delicate branches ascend- 

 ing or spreading, 2 to 3 cm long; spikelets 1.5 to 2 mm long, the capil- 

 lary pedicels longer than the spikelets; glumes acute, about two thirds 

 as long as the lemma, sparsely hirsute; lemma minutely silky on mid- 

 nerve and margins below, 2-lobed, the delicate awn 1 to 2 mm long. 

 G — Open gravelly places, western Texas and New Mexico to north- 

 ern Mexico. 



2. Muhlenbergia microsperma (DC.) Kunth. Littleseed muhly. 

 (Fig. 733.) Annual; culms densely tufted, branching and spreading at 

 base, often purple, 10 to 30 cm tall; blades mostly less than 3 cm long, 1 



