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Annuals or perennials. Leaf blades narrow, flat; ligule a line of hairs, sometimes from a membranous base. Inflorescence linear, cylindrical, spikelike, dense, axis bearing numerous very short racemes; racemes subsessile or shortly pedunculate, falling entire as spiny burrs; spikelets 2–5, contiguous or on a short rachis, sometimes the upper reduced. Spikelets elliptic to lanceolate, floret 1; lower glume a tiny scale or suppressed; upper glume as long as spikelet, rounded, prominently 5–7-veined, veins forming ribs armed with conspicuous, stout, hooked spines, thin between ribs, apex acute to acuminate; lemma ovate, almost as long as glume, flattened, membranous, 3-veined, pubescent around midvein, apex entire; palea slightly shorter than lemma. Caryopsis ellipsoid to oblong, slightly dorsally compressed.
Annuals or perennials. Leaf-blades flat, pectinate-ciliate on the margins; ligule a line of hairs. Inflorescence stiff, dense, cylindrical, spike-like, the spikelets in subsessile (rarely long peduncled) deciduous clusters; each cluster composed of 2–5 spikelets, these paired, or sessile upon a very short rhachis. Spikelets lanceolate to ovate, awnless, those of a cluster all alike or the upper ± reduced; glumes dissimilar, the lower (adaxial) a tiny hyaline scale or suppressed; upper glume as long as the spikelet, its nerves formed into prominent ribs bearing a row of stout prickles, thin between the ribs; lemma almost as long as the glume, ovate, membranous, 3-nerved; stamens 3. Caryopsis ellipsoid to oblong, slightly dorsally compressed.
Spikelets 1-flowered, awnless; glumes very unequal, the inferior small or suppressed, nerveless, the superior as long as the spikelet, its nerves formed into prominent ribs, these bearing a row of stout prickles; lemma shorter than the spikelet, membranous, 3-nerved.
Inflorescence a cylindrical false raceme; racemelets shortly or rarely long pedunculate, deciduous, comprising 2–5 spikelets, these paired or sessile on a very short rhachis, the uppermost reduced.
Caryopsis ellipsoid to oblong, slightly dorsally compressed.
