marshy or aquatic herbs with creeping rhizomes. Leaves erect, linear,
distichous, usually spongy, margin entire, sheathed at base. Inflorescence a
terminal, cylindric spike, bearing numerous, minute, densely crowded unisexual
flowers with lower part female, upper part male. Perianth absent. Male flowers:
consisting of 1-3 stamens, connate, filaments short, anthers 2-thecous,
basifixed, longitudinally dehiscent. Female flowers: carpel 1, ovary fusiform
on gynophore, styles capillary, stigmas broadened or spatulate, ovule 1. Fruit
follicle, minute, fusiform, falling off together with stalk.