Annuals or perennials. Leaf-sheath compressed. Ligule reduced to ciliate rim. Leaf-blade flat or involute. Culm terete, solid. Inflorescence a solitary spike-like panicle of prickly glomerules, composed of coalescing spines; spikelets sessile, solitary, or in clusters of 2-5 surrounded by, and deciduous with the sessile or minutely peduncled involucre of ± connate, often rigid, antrorsely or retrorsely scabrid spines or bristles. Spikelets 2-flowered; lower floret ♂, or Ø and reduced to a lemma, upper floret ☿. Glumes usually dissimilar, rarely subequal, hyaline or thinly membranous; lower often 0, or if present, 1-5-nerved, upper ≤ spikelet, 1-5-(7)-nerved. Lower floret: lemma usually similar in texture to upper glume and ≈ spikelet, 3-7-nerved; palea ≈ lemma, 2-keeled. Upper floret: lemma = spikelet, firmly membranous, chartaceous or coriaceous, 5-7-nerved; palea = lemma; lodicules 0; stamens 3; ovary apex glabrous, styles terminal, free, or connate below; caryopsis dorsiventrally compressed, glabrous, embryo c. ⅔ length of caryopsis, hilum basal, punctiform.

Tufted or rhizomatous or straggling perennials; or annuals. Leaf-sheath loose, usually open. Ligule usually a ciliate rim, rarely membranous. Leaf-blade linear to lanceolate, flat, folded or convolute. Culm simple or much-branched. Inflorescence usually a dense, spike-like panicle with very numerous, very short branches falling with spikelets at maturity, and usually leaving scars on the rachis; rarely reduced to a few spikelets. Spikelets 2-flowered, solitary or in groups of 2 or 3 surrounded by an involucre of unequal glabrous or plumose bristles united at base; spikelets and bristles shed freely at maturity; lower floret ♂ or Ø, with or without palea, rarely ☿; upper floret ☿, or sometimes ♂ in lateral spikelets of a cluster. Glumes membranous, subequal, or the lower smaller, sometimes minute or 0; lower (0)-1-3-nerved, upper ≤ spikelet, (0)-1-9-nerved. Lower floret: lemma ≤ spikelet, membranous, (0)-3-9-(15)-nerved, enclosing narrow palea, or palea 0. Upper floret: lemma ≈ spikelet, chartaceous, (3)-5-7-(15)-nerved, glabrous or sometimes pubescent near margins; palea ≈ lemma and of similar texture; lodicules minute or 0; stamens 3, anthers occasionally penicillate; ovary apex glabrous, styles ± terminal, free or ± connate; caryopsis dorsiventrally compressed, embryo large, hilum punctiform.