MANUAL OF THE GRASSES OF THE UNITED STATES 



365 



date, minutely pubescent. 91 —Prairies and gravelly or stony 

 slopes, Michigan, Wisconsin to Alberta, south to Ohio and New 

 Mexico (fig. 745). 



11. Muhlenbergia wrightii Vasey. Spike muhly. (Fig. 746.) 

 Culms closely tufted from a hard crown, erect, wiry, 30 to 60 cm tall; 

 sheaths compressed-keeled; ligule 1 to 2 mm long, sometimes longer; 

 blades flat, 1 to 3 mm wide; panicle spikelike, interrupted below, 5 to 

 10 cm long; spikelets about 2.5 mm long, the glumes rather thin, 

 mostly about half as long as the spikelet, broad at base, tapering to 

 an awn point; lemma glabrous, acuminate, awn-tipped. % — 

 Plains and open slopes at medium altitudes, Colorado, Utah, New 

 Mexico, Arizona, and northern Mexico (fig. 747). 



12. Muhlenbergia arenacea (Buckl.) Hitchc. (Fig. 748.) Peren- 

 nial, with creeping rhizomes; culms tufted from the branches of the 



Figure 741.— Muhlenbergia thurberi. Plant, X 1; 

 glumes and floret, X 10. (Standley 7345, Ariz.) 



Figure 743.— Muhlenbergia curtifolia. Plant, X 1 

 glumes and floret, X 10. (Type.) 



rhizomes, sometimes decumbent at base, 10 to 20 cm tall; ligule 

 prominent, decurrent, 1 to 2 mm long, the margins usually split 

 away, forming an erect auricle at each side; 

 blades flat, wavy, mostly 1 to 3 cm long, about 

 1 mm wide, sharp-pointed, the margins and 

 midnerve white and cartilaginous; panicle 

 diffuse, 7 to 12 cm long, about as broad, the 

 branches and pedicels capillar}- spikelets 

 about 2 mm long, rarely 2-flowered; the glumes 

 about half as long, abruptly apiculate or suba- 

 cute ; lemma glabrous, abruptly mucronate. % 

 (Sporobolus auriculatus Vasey.) — Low places in mesas, Texas to 

 Arizona and Sonora. This species and the next three are placed in 

 Muhlenbergia because of the 3-nerved mucronate lemma. The 



Figure 742.— Distribution of 

 Muhlenbergia thurberi. 



