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.