The Manual of the Botany of the Northern United States / Including the District East of the Mississippi and North of North Carolina and Tennessee

by Asa Gray

27. Alopecurus. Lower glumes united at base, the flowering awned on the back. Palet none. Spike cylindric.

[*][*][*] Glumes membranous, the lower rarely strongly complicate, the flowering with a dorsal awn or awnless; spikelets variously panicled.—Agrosteæ.

[+] Flowering glume 1- (rarely 3-) nerved, awnless; grain loosely enclosed or naked.

28. Sporobolus. Culms wiry or rigid. Leaves involute.

[+][+] Flowering glume 3–5 nerved, mostly awned; grain enclosed.

[++] Rhachis not reduced above the single flower.

29. Agrostis. Spikelets in an open panicle.

30. Polypogon. Empty glumes long-awned. Panicle spike-like.

31. Cinna. Spikelets flattened, in a loose panicle. Palet 1-nerved. Stamen 1

[++][++] Rhachis bearing a rudimentary second flower or short bristle (except in species of n. 33).