MANUAL OF THE GRASSES OF THE UNITED STATES 373 



Lower sheaths compressed keeled 65. M. lindheimeri. 



Lower sheaths not compressed keeled 64. M. longiligula. 



9b. Lemma with an awn usually more than 5 mm. long, or some of the awns less 

 in M. dubioides and M. metcalfei. 

 Old sheaths becoming flat and more or less coiled at base of plant. 



47. M. VIRESCENS. 



Old sheaths not flat and coiled. 

 Panicle mostly 20 to 40 cm. long. 



Ligule 1 to 2 mm. long; glumes acute or awn-pointed. 



59. M. DUBIOIDES. 

 Ligule 4 to 5 mm. long; glumes obtuse to subobtuse. 



57. M. METCALFEI. 



Panicle mostly 5 to 10 cm. long. 



10a. Lemma pilose or villous on lower part. 

 Culms loosely tufted, hard and wiry at base. 



Glumes and floret about equal; lemma 2.5 to 3 mm. long, villous 



below 21. M. polycaulis. 



Glumes about half as long as floret; lemma 4 to 5 mm. long, sparsely 



pilose 23. M. arsenei. 



Culms closely or somewhat loosely tufted, slender but not hard and 



wiry at base 48. M. monticola. 



10b. Lemma scaberulous, not pilose. 



Glumes less than 1 mm. long 49. M. parviglumis. 



Glumes 2 to 4 mm. long 22. M. pauciflora. 



8b. Panicle open, or at least loose, the branches naked at base (sometimes shortly 

 so in M. metcalfei). 

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



51. M. PORTERI. 



Plants erect, not widely spreading and much branched. 

 Blades flat, the midnerve and margins white-cartilaginous. 



52. M. ARIZONICA. 

 Blades folded or involute, or occasionally some of them flat. 

 Blades short in a basal cluster. 



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



curled or falcate 53. M. torreyi. 



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



flat or usually folded 54. M. arenicola. 



Blades elongate. 



11a. Panicle open or diffuse, if narrow, the branches slender; capillary, 



more or less flexuous. 



Awn of lemma less than 5 mm. long; panicle usually not more than 



twice as long as wide at maturity, the branches and pedicels stiff. 



Plants fibrous at the base; lemma awnless or with an awn to 2 mm., 



rarely to 5 mm., long 60. M. expansa. 



Plants not fibrous at base; lemma with an awn 2 to 5 mm. long. 



61. M. REVERCHONI. 



Awn of lemma usually more than 10 mm. long (sometimes awnless in 

 M. emersleyi); panicle elongate, usually at least 4 times as long as 

 wide at maturity. 

 Panicle diffuse, the branches more than 10 cm. long; pedicels usually 



much longer than the spikelets 62. M. capillaris. 



Panicle open but not diffuse. 



Panicle deep purple; blades relatively coarse, some of them usually 



flat 63. M. rigida. 



Panicle pale or tawny; blades involute, scabrous. 

 Ligule 4 to 10 mm. long; glumes obtuse to subacute. 



55. M. SETIFOLIA. 



Ligule 1 to 3 mm. long; glumes acute to mucronate. 



56. M. XEROPHILA. 



lib. Panicle narrow, elongate, the branches rather stiffly ascending or 



appressed. 



Lower sheaths rounded 57. M. metcalfei. 



Lower sheaths compressed-keeled. 



Glumes as long as the floret; lemma villous below. 



67. M. EMERSLEYI. 



Glumes distinctly shorter than the floret; lemma pubescent on the 

 margins toward the base 66. M. involuta. 



