15. Scleria P.J. Bergius (nut grass, nut rush)

Plants annual or perennial with rhizomes, monoecious. Aerial stems 1 to several per plant, erect to ascending, less commonly lax and supported by other vegetation, unbranched below the inflorescence, 3-angled. Leaves alternate, the lowermost ones often lacking leaf blades, the sheath without a ligule, but the upper edge opposite the leaf blade often convex and with a scarious, sometimes hairy tip (called a contraligule by some botanists), the leaf blade erect to ascending or sometimes spreading, the midvein usually thickened on the undersurface. Inflorescences terminal and also less commonly axillary in some species, composed of few to several dense clusters of spikelets, these headlike or in an interrupted spike, subtended by reduced, leaflike bracts. Staminate and pistillate spikelets usually mixed in the same cluster. Staminate spikelets with 2–5 fertile florets, the scales lanceolate to narrowly ovate, narrower than those of the pistillate spikelets, the tips narrowly pointed, glabrous or hairy, the lowermost sterile scale occasionally subtending a pistillate spikelet. Pistillate spikelets with the uppermost floret fertile, the several lower scales empty, ovate, somewhat broader than those of the staminate spikelet, the midrib usually extended past the tapered point as an awn, glabrous or hairy. Perianth (bristles or scales) absent. Stamens 1–3. Styles sometimes somewhat enlarged at the base, not persisting on the fruit as a tubercle. Stigmas 3. Ovaries and fruits naked, without a perigynium (saclike covering). Fruits appearing hard, white, and bony at maturity, circular to obtusely triangular in cross-section, circular to broadly elliptic in outline, in most species with a specialized basal disk (the hypogynium), this variously circular to angled or lobed, sometimes also with 3–9 variously shaped tubercles. About 225 species, nearly worldwide, but most diverse in tropical regions.