MANUAL OF THE GRASSES OF THE UNITED STATES 365 



date, minutely pubescent. 01 —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; hgule 

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



aw r ay, forming an erect auricle at each side; 

 blades flat, w T avy, mostly 1 to 3 cm long, about 

 1 mm wide, sharp-pointed, the margins and 

 midnerve wmite and cartilaginous; panicle 

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

 branches and pedicels capillary; 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. 



