Annual or perennial herbs. Rhizomes slender, spreading, scale leaves and erect leafy shoots at nodes. Leaves opposite or in pseudowhorls; with sheathing stipule not adnate to leaves, the distal part forming a ligule, ligule longer than sheathing base; lamina linear. Flowers subsessile. Male flowers lacking perianth; borne at base of female flowers; anther mass on slender filament. Female flowers with cup-like perianth; 1–9 free carpels, each with 1 ovule; style slender. Fruit with flattened tubercules on dorsal surface; style persistent.
Cosmopolitan genus with 1–5 species; 1 native in Australia and Victoria.
