Plants annual; synoecious. Culms 1-75 cm, erect to geniculately ascending, sometimes branching above the base; nodes usually exposed. Sheaths open, often becoming inflated, junction with the blades evident; ligules of hairs; auricles absent; blades often disarticulating. Inflorescences terminal or terminal and axillary, spikelike or capitate panicles subtended by, and often partially enclosed in, 1 or more of the uppermost leaf sheaths, additional panicles often present in the axils of the leaves below. Spikelets 2-6 mm, strongly laterally compressed, with 1 floret; florets bisexual; disarticulation above or below the glumes. Glumes 1-veined, strongly keeled; lemmas membranous, glabrous, 1-veined, strongly keeled, not lobed, unawned, sometimes mucronate; paleas hyaline, 1-2-veined; lodicules absent; anthers 2 or 3; ovaries glabrous. Fruits oblong, pericarp loosely enclosing the seed and easily removed when wet; hila punctate. x = 8. Name from the Greek krupsis, concealment, alluding to the partially concealed inflorescence.
Spikelets 1-fld, articulated above the glumes; glumes compressed and keeled, subequal, 1-veined, acute, scarious-margined; lemma membranous, somewhat longer than the glumes, 1-veined, awnless; palea about as long as the lemma; low annuals with erect to decumbent or prostrate stems, short blades, and dense, short, spike-like panicles of small spikelets; ligule a zone of hairs. (Heleochloa) 10, Old World.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.