Perennial, caespitose or rhizomatous; branching intravaginal or extravaginal. Culm simple or bambusiform, sometimes branching at nodes. Inflorescence a narrow or open, much-branched panicle. Spikelets 1-flowered; disarticulation oblique above persistent glumes. Glumes 2, equal or unequal, enclosing the floret, lower longer, 1-3-5-nerved, acute, acuminate, rarely mucronate, awned, or erose. Flower ☿. Lemma cylindrical, coriaceous, indurated, fusiform, pyriform or turbinate, pubescent, hairy or tubercular-scabrid or both, 5-nerved (7- in A. flavescens), margins overlapping, terminating in a rim with or without a coma of longer hairs; lobes small or 0. Awn 0-1-2-geniculate, often very long; column twisted, arista straight or curved. Callus sharply pointed (blunt in A. verticillata), hairs usually different in colour and density from those of lemma, extending over lemma base. Palea enclosed by lemma, membranous, hyaline or ± indurated, ≤ lemma, 2-nerved, internerve hairy or glabrous. Lodicules 2 or 3, hyaline, glabrous. Stamens 3, anthers penicillate or naked at apex and/or caudate at base; in cleistogamous flowers reduced to 1 small fertile anther and 2 sterile small anthers. Gynoecium: ovary glabrous, stigmas plumose. Caryopsis tightly enclosed and conforming to shape of lemma; embryo to about ⅓ of caryopsis; hilum linear, ≈ caryopsis. Flowering chasmogamous or cleistogamous in aerial inflorescences. Fig. 5.