Plants annual or perennial; rhizomatous, rhizomes slender, terminating in a reduced panicle of cleistogamous spikelets. Culms 30-100 cm, erect or decumbent. Sheaths open; auricles absent; ligules of hairs; blades flat. Inflorescences subterranean and aerial, only the subterranean inflorescences forming mature caryopses; subterranean panicles with 1-5 spikelets; aerial panicles terminal, simple, with elongate rachises bearing erect to ascending branches, usually with 15 or more spikelets. Spikelets glabrous, unawned, with 2 florets. Subterranean spikelets setting seed, with 1 glume; lower glumes absent; upper glumes and lower lemmas similar in size and texture, exceeded by the upper florets; upper florets turgid, ellipsoidal; upper lemmas mostly indurate, margins thin, flat, apices acuminate; upper paleas similar in texture to the lemmas; anthers 3; caryopses well-developed. Aerial spikelets not setting seed, sometimes forming immature caryopses, lanceoloid, dorsally compressed to terete; glumes unequal or the lower glumes absent; upper glumes and lower lemmas similar in size and texture; upper lemmas mostly indurate, margins thin, flat, apices acute; lower florets staminate or sterile; upper florets with pistils but fruit not developed. x = 9. Name from the Greek amphikarpos, doubly fruit-bearing, a reference to the two kinds of spikelets.

Spikelets dimorphic; aerial spikelets in narrow terminal panicles, with a single perfect but often sterile terminal fl and a lateral floret represented only by a glume-like sterile lemma; first glume short or obsolete; second glume and sterile lemma subequal, about as long as the cartilaginous second lemma; fertile lemma with scattered short hairs; subterranean spikelets plump, fusiform, fertile, solitary at the end of a slender elongate branch, the first glume lacking, the second glume and sterile lemma several-veined, equaling the indurate fertile lemma; annual or perennial grasses with relatively short lvs and ciliate ligule. 2, the other in se. U.S.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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