FLOWERING PLANTS AND FERNS OF ARIZONA 115 



23. Blades involute; culms loosely tufted, sometimes forming large 

 cushions, erect from a decumbent base (24) . 

 24. Panicles mostly less than 15 cm. long; blades 1 to 4 cm. long, 



curled or falcate 31. M. torreyi. 



24. Panicles mostly more than 20 cm. long; blades commonly 5 to 8 



cm. long 32. M. arexicola. 



22. Leaf blades elongate, much more than 8 cm. long (25). 



25. Basal sheaths strongly compressed-keeled; glumes nearly as long 



as the lemma 35. M. emersleyi. 



25. Basal sheaths rounded on the back; glumes much shorter than the 

 lemma (26) . 

 26. Panicles pale or tawny, the slender branches flexuous, ascending 

 or spreading; glumes about half as long as the lemma; awn 



of the lemma 18 to 25 mm. long 33. M. xerophila. 



26. Panicles dark purple, the capillary branches finally spreading; 

 glumes not more than one-fourth as long as the lemma; awn 



of the lemma 10 to 15 mm. long 34. M. rigida. 



20. Panicles narrow, dense or spikelike, the branches floriferous from the 

 base (27). 

 27. Awn usually less than 5 mm. long, occasionally as much as 10 mm. 

 long or the lemma sometimes awnless (28). 

 28. Panicles spikelike (29). 



29. Leaf blades flat, 1 to 3 mm. wide; panicles 5 to 15 cm. long; glumes 

 awn-pointed, distinctly shorter than the lemma. 



20. M. WRIGHTII. 



29. Leaf blades involute; panicles 10 to 30 cm. long; glumes acute or 



obtuse, nearly as long as the lemma 21. M. rigexs. 



28. Panicles dense but loosely flowered, never spikelike (30). 



30. Spikelets 2 to 3 mm. long; glumes nearly as long as the awnless 



lemma 22. M. loxgiligula. 



30. Spikelets about 4 mm. long; glumes half to two-thirds as long as the 

 lemma, the latter with an awn 3 to 10 mm. long. 



23. M. DUBIOIDES. 



27. Awn 10 mm. long or longer (31). 



31. Second glume 3-toothed: lemma often yellowish: leaves mostly basal, 



the sheaths becomins; flat and loose 24. M. Montana. 



31. Second glume entire (32). 



32. Old sheaths flat and more or less coiled at base of the plant : spike- 

 lets about 5 mm. long; glumes nearly as long as the lemma. 



25. M. VIRESCEXS. 

 32. Old sheaths never flat or coiled (33). 



33. Lemma 4 mm. long, scaberulous; glumes about half as long as 



the lemma, acuminate or awn-tipped _ 28. M. pauciflora. 



33. Lemma 2.5 to 3 mm. long, pilose on the lower part; glumes at 



least two-thirds as long as the lemma (34). 



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



villous toward base 26. M. polycaulis. 



34. Culms usually densely tufted, slender, not wiry at base; 

 floret densely pilose at base 27. M. moxticola. 



1. Muhlenbergia pectinata C. O. Goodding, Wash. Acad. Sei. Jour. 



31: 505. 1941. 



Mule Mountains (Cochise County) and Sycamore Canyon (Santa 

 Cruz County), wet places below and on the face of cliffs, September. 

 Southeastern Arizona to Jalisco. A delicate spreading annual with 

 narrow panicles and ciliate lemmas, related to M. ciliata (DC.) 

 Kunth. 



2. Muhlenbergia microsperma (DC.) Kunth, Rev. Gram. 1: 64. 1829. 



Trichochloa microsperma DC, Cat. Hort. Monsp. 151. 1813. 



Mohave, Pinal, Maricopa, Pima, and Yuma Counties, 5,000 feet 

 and lower, rocky slopes and canyons, February to May and at other 

 times after rains. Arizona and southern California to Peru. 



