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



Glumes with stiff scabrous awn-tips, much exceeding the awnless lemma; pan- 

 icles terminal on the culm or leafy branches, compact, interrupted, bristly. 

 Culms mostly simple or branching at base; internodes minutely puberulent; 



sheaths not or scarcely keeled 32. M. glomerata. 



Culms subcompressed, mostly branching from the middle nodes; internodes 

 smooth and glossy except at summit; sheaths keeled. 



33. M. RACEMOSA. 

 Glumes acuminate, sometimes awn-tipped but not stiff and exceeding the lemma; 

 panicles terminal and axillary, numerous, not bristly. 

 Culms glabrous below the nodes; panicles not compact, the branches ascend- 

 ing; plants sprawling, top-heavy, the branchlets geniculate-spreading. 



38. M. FRONDOSA. 

 Culms strigose below the nodes; panicles compact or if not the branches erect 

 or nearly so; plants often bushy-branching but not sprawling with genicu- 

 late branchlets. 

 Callus hairs wanting; lemma nearly smooth, awnless. 



39. M. GLABRIFLORA. 



Callus hairs present; lemma pubescent below. 



Panicles not compactly flowered; lemma with awn as much as 10 mm. or 

 more long (nearly awnless in forma attenuata); some of the blades 



10 to 15 cm. or more long 40. M. sylvatica. 



Panicles compactly flowered or, if not, lemma awnless; blades commonly 

 less than 10 cm. long, but sometimes longer. 



Sheaths glabrous _ 41. M. mexicana. 



Sheaths scabrous 34. M. californica. 



3b. Rhizomes wanting, the culms tufted, usually erect. 

 7a. Culms decumbent and rooting at the nodes. 



Spikelets awnless; panicles open, diffuse 29. M. uxiflora. 



Spikelets awned ; panicles narrow, the branches ascending or appressed. 



Glumes minute, the first sometimes wanting _ 42. M. schreberi. 



Glumes evident, as much as 3 mm. long (see also M. schreberi var. palustris). 



Awns 1 to 2 mm. long 43. M. curtisetosa. 



Awns 5 to 20 mm. long 22. M. pauciflora. 



7b. Culms erect or spreading, but not rooting at the nodes. 

 Second glume 3-toothed (rarely not toothed in M . filiculmis). 



Lemma 4 mm. long; culms relatively stout, 15 to 60 cm. tall.... 45. M. Montana. 

 Lemma 2.5 to 3 mm. long; culms filiform, 10 to 20 cm. tall.... 46. M. filiculmis. 

 Second glume usually acute or awned, sometimes erose-toothed, not distinctly 3- 

 toothed. 

 8a. Panicle narrow or spikelike, the branches floriferous from the base or nearly 

 so (see also M . metcalfei). 

 9a. Lemma acute, acuminate, mucronate or short-awned. 

 Blades involute. 



Panicle elongate and spikelike. 



Glumes and lemma or some of them awn-tipped 70. M. marshii. 



Glumes acute to blunt or erose; lemma not awn-tipped. 



Ligule 2 to 3 mm. long; lower panicle branches sometimes 5 to 10 cm. 



long _ _ 68. M. rigens. 



Ligule 1 to 2 mm. long; lower panicle branches seldom more than 3 cm. 



long 69. M. MUNDULA. 



Panicle narrow but scarcely spikelike, the branches loosely flowered. 

 Blades mostly in a short basal cluster; panicle 5 to 8 cm. long. 



44. M. jonesii. 

 Blades not in a short basal cluster; panicle 10 to 30 cm. long. 



58. M. DUBIA. 

 Blades flat, folded, or loosely involute. 

 Panicle more or less spikelike. 



Glumes obtuse; culms delicate. Ligule about 2 mm. long. 



13. M. FILIFORMIS. 

 Glumes acute or acuminate ; culms wiry. 



Glumes gradually acute; culms minutely pubescent; ligule about 0.5 



mm. long 24. M. cuspidata. 



Glumes abruptly acute, usually awn-pointed or awned; culms hispidu- 



lous; ligule 1 to 3 mm. long 25. M. wrightii. 



Panicle narrow, but not spikelike. 



Lemma villous below 67. M. emersleyi. 



Lemma glabrous or obscurely pubescent. 



