114 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



4. Glumes glabrous (5). 



5. Panicle branches closely appressed, densely flowered; spikelets ap- 

 pressed; lemma ciliate, the awn 10 to 30 mm. long; glumes awn- 

 pointed 1. M. PECTINATA. 



5. Panicle branches ascending, loosely flowered; spikelets somewhat spread- 

 ing; lemma not ciliate, the awn 10 to 30 mm. long; glumes obtuse; 

 lower sheaths inflated, enclosing cleistogamous spikelets. 



2. M. MICROSPERMA. 



1 . Plants perennial (6) . 



6. Plants with prominent scaly creeping rhizomes: See also M. polycaulis (7). 

 7. Panicles open; spikelets on slender, rather long, usually spreading pedi- 

 cels (8). 

 8. Panicle branches 3 to 5, divided into fascicles of capillary, finally spread- 

 ing, very scabrous branchlets; awn 1 to 1.5 mm. long; leaf blades 



short, sharp-pointed, involute 6. M. pungens. 



8. Panicle branches numerous, the branchlets not arranged in fascicles; 

 spikelets 1 to 2 mm. long; lemma acute or mucronate; leaf blades 

 flat, relatively soft (9) . 



9. Ligule 1 to 2 mm. long, auriculate 7. M. arenacea. 



9. Ligule minute, without auricles 8. M. asperifolia. 



7. Panicles narrow, often condensed; spikelets short pediceled (10). 



10. Leaf blades flat, at least some of them more than 3 mm. wide, lax, 

 spreading (11). 

 11. Callus hairs copious, as long as the lemma; panicles silky, often tinged 



with purple 16. M. axdina. 



11. Callus hairs rather sparse, not more than half as long as the lemma 

 (12). 

 12. Glumes awned, the awns exceeding the awnless floret; panicles com- 

 pact, bristly 17. M. racemosa. 



12. Glumes acuminate or awn-pointed but not exceeding the lemma; 

 panicles not bristly (13). 

 13. Lemma awnless; panicles compactly flowered; blades mostly 



less than 10 cm. long 18. M. foliosa. 



13. Lemma awned, the awn 5 to 10 mm. long; panicles rather loosely 



flowered 19. M. sylvatica. 



10. Leaf blades involute or, if flat, then less than 2 mm. wide (14). 



14. Culms 1 to 3 meters high, woody at base, as much as 6 mm. thick, 

 freely branching at the middle and upper nodes- _ 9. M. dumosa. 

 14. Culms not more than 60 cm. high, usually much less (15). 



15. Leaf blades 5 to 15 cm. long, flat; culms 30 to 60 cm. high, slender, 

 branching from the lower nodes; awn of the lemma 1 to 6 mm. 



long 15. M. GLAUCA. 



15. Leaf blades mostly much less than 5 cm. long (16). 



16. Culms widelv creeping; blades conspicuously recurved-spread- 

 ing (17). 

 17. Spikelets about 3 mm. long 10. M. repens. 



17. Spikelets about 2 mm. long 11. M. utilis. 



16. Culms erect or decumbent at base, but not widely creeping (18). 



18. Culms nodulose-roughened; glumes about half as long as the 



floret; ligule 2 to 3 mm. long 12. M. richardsonis. 



18. Culms glabrous or pubescent, but not nodulose (19). 



19. Lemma mucronate or short-awned; plants forming dense 

 cushions, the leaves crowded toward base. 



13. M. THURBERI. 

 19. Lemma with an awn 1 to 5 mm. long; plants forming loose 

 bunches, the leaves not crowded toward base. 



14. M. CURTIFOLIA. 

 6. Plants tufted; rhizomes wanting: See also M. glauca (20). 



20. Panicles open or at least loose, the branches naked at base (21). 

 21. Culms wiry, freely branching, geniculate, widely spreading. 



29. M. PORTERI. 

 21. Culms erect or sometimes decumbent at base, but not widelv spread- 

 ing (22). 

 22. Leaf blades rarely more (usually much less) than 8 cm. long; culms 

 rather freely branching at the lower nodes (23) . 

 23. Blades flat or folded, with a conspicuous firm white midnerve and 

 margins 30. M. arizonica. 



