Prairie grass (Brome grass)
Bromus unioloides (Bromus catharticus)

Annual or biennial; culms erect or spreading, 6-10 dm. tall; sheaths pilose or glabrous; blades glabrous or sparsely pilose, ca. 3-6 mm. wide; panicle 1-1.3 dm. long, the branches stiff, in 2's or 3's bearing sessile spikelets; spikelets much compressed, 5-13 fld., 1-3 cm. long, the rachilla disarticulating above the glumes and between the florets; glumes 7-12 mm., 5-9 nerved; lemmas 10-12 mm. long; 9-11 nerved,  finely scabrous-pubescent; awn 0-2.5 mm.