Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Spikelets 1-fld, articulated above the glumes; glumes membranous, linear to lanceolate, 1(2–5)-nerved, acute, acuminate, or short-awned, the first sometimes deciduous; lemma indurate, linear, obscurely veined, closely convolute about the palea and grain, often scabrous on the obscure keel or toward the tapering summit, and with a sharp, usually bearded callus; awns of the lemma normally 3, elongate, similar or dissimilar; annual or perennial, often weedy, often branched from some or all the nodes, with narrow, often involute lvs, minute ligule, and terminal, usually slender or spike-like, dense or lax panicles or racemes. The awns, erect and parallel when immature or moist, diverge when dry and mature into characteristic positions. Lengths of the glumes and lemmas are here measured from the base of the spikelet. 200, mainly warm reg.