Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Spikelets 2–5-fld, turgid, borne flatwise singly and fitting closely into alternate hollows on 2 sides of the rachis, the joints thickened and exposed at the top, the whole spike compact and cylindrical, at maturity breaking off at the base or disarticulating into joints; glumes indurate, many-veined, not or scarcely keeled, 2–4-toothed at the truncate tip, 1 or more of the teeth sometimes produced into an awn; lemmas rounded on the back, indurate above, the veins not convergent, toothed at the truncate summit, one or more of the teeth often prolonged into an awn; caryopsis furrowed on the back, hairy at the top; annual grasses with flat lvs. 15, Medit. reg. and w. Asia.