Muhlenbergia arizonica
Plants perennial; cespitose, not rhizomatous. Culms 15-50 cm, erect to decumbent; internodes hispidulous or glabrous below the nodes. Sheaths from slightly shorter to slightly longer than the internodes, rounded to somewhat flattened but not keeled, hispidulous basally, glabrous distally, margins hyaline, not becoming spirally coiled when old; ligules 1-2 mm, hyaline, obtuse, minutely erose; blades 4-7 cm long, 0.8-2 mm wide, flat or folded, glabrous abaxially, scabridulous or hispidulous adaxially, midveins and margins conspicuous, thickened, white, and cartilaginous. Panicles 4-20 cm long, 4-15 cm wide, diffuse; primary branches 0.5-7.5 cm, capillary, diverging 40-90° from the rachises, naked basally; pedicels 2-16 mm, flexuous. Spikelets 2.1-3.1 mm. Glumes equal, 1-1.5 mm, 1-veined, apices scabridulous, obtuse to acute, some¬times minutely erose, unawned; lemmas 2-3.1 mm, elliptic, purplish, appressed-pubescent on the lower 3/4 of the midveins and margins, hairs to 0.6 mm, apices scabrous, acute, minutely bifid, awned, awns 0.5-1.1 mm; paleas 2.1-3.2 mm, elliptic, glabrous, acute; anthers 1.6-2.1 mm, purplish. Caryopses 1.3-1.7 mm, fusiform, sulcate dorsally, brownish. 2n = 20.
Discussion
Muhlenbergia arizonica grows in sandy drainages and gravelly canyons, and on plateaus and rocky slopes in open desert grasslands, at elevations of 1220-2230 m. Its range extends from the southwestern United States into northwestern Mexico. Flowering is from August to October.
Selected References
None.