Perennials, caespitose or with short rhizomes, bisexual. Ligule a fringe of hairs. Inflorescence a dense spike-like or head-like panicle; often with the one to several lowest spikelets sterile, sometimes reduced to glumes, sometimes involucre-like. Spikelets ±sessile to pedicellate, usually not noticeably compressed, occasionally slightly laterally or dorsiventrally compressed, with 1 bisexual floret, with no sterile or reduced florets, disarticulating above glumes; rachilla not prolonged. Glumes 2, ±equal, awned to awnless, rounded to flat on back, sometimes with 2 folds or keels midway between midline and margins, or with a single midline keel (in A. setaceus), 3-nerved (1 in A. setaceus), with lateral nerves often close to midnerve and often faint. Lemma deeply cleft, with 3 acute to long-awned lobes, becoming firmer than glumes with maturity but not indurate, not keeled or occasionally with 2 lateral keels, 3-nerved, variously indumented; awns 3, equal, subequal or very unequal with the central one better developed. Palea ±equal to lemma, slightly narrower, with similar indumentum, with 2 awns or lobes resembling and often equalling those of lemma, rounded on back, 2-nerved. Hilum punctiform to shortly elliptic.
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