or seldom annual herbs, caespitose, emergent from shallow-water, or seldom
fully submerged. Leaves mostly linear, grasslike, basally crowded.
Inflorescence small head, subtended by involucre of bracts. Peduncle usually exceeding leaves. Flowers small, sessile
or shortly pedicellate, unisexual, males
and females often mixed, or males in middle and females around. Perianth shaffy
or membranous, segments 2-3-merous, biseriate, outer free, inner often
stipitate and cupular. Stamens equal or double perianth-number, rarely fewer,
filaments free, anthers 1-2-locular, dehiscing vertically. Ovary 2-3 loculed, superior, style lobed,
ovules solitary, placentation axile. Fruit membranous capsule, 2-3 celled,
dehiscent. Seeds solitary, pendulous, with copious endosperm and embryo.