Perennial, tufted herbs. Stem erect,
mostly triquetrous, rarely subterete, often clothed at the base by persistent
leaf sheaths or their fibrous remains. Leaves tristichous, usually narrowly
linear, sheathing at base, with a ligule at the junction of blade and sheath.
Inflorescence panicles, racemes or spikes, more rarely reduced to a single
spikelet. Spikelets terete, sessile or peduncled, few-many flowered, wholly
male or wholly female or bisexual. Bracts foliacious or glume-like. Flower
unisexual. Male flower consisting of three free stamens. Female flowers
consisting of a single pistil enclosed in a bottle shaped prophyll; stigmas 2
or 3. Utricles membranous, beakless to strongly beaked. Fruit a nut, trigonous
or lenticular, enclosed within the utricle.