Submerged perennials forming large colonies, found in fresh or brackish water, the upper parts dying down in cold or dry spells. Rhizome persistent, forming scaly winter buds ("Unions"), much branched, with numerous long fine roots arising in whorls from the nodes, the roots bearing long root-hairs. Stems varying in length in proportion to depth of the water, branching freely, terete, slender. Leaves all submerged, often bunched above and spreading in a fan-shaped manner; stipules attached to the lamina, forming a folded sheath, often with whitish margins and terminating above in a large, rounded deciÂduous ligule; lamina usually curved ou.wards above the sheath, linear to filiform, 4-12 cm long and 1-2 mm broad, translucent, with cross-bars, if broad with lateral longitudinal veins, apex acute or rounded and apiculate. Spikes lengthening during anthesis and the fruiting stage, the lower flowers especially wide'y spaced, scape wiry, thin, whorls 4-8, consisting of 2-4 flowers each, stigmas large (the pollen or detached flowers floating on the water and thus contacting the large papillae on the stigmas). Fruit c. 4 mm long, yellowish-brown, convex, dorsally with 2 distinct broad lateral keels sloping inwards to the ventral straight keel, beak short. Fig. 15 : 1.
