Aquatic herbs, floating, submerged or marshy with creeping rootstock; stem terete, brownish or pale purple, creeping, smooth, branched; leaves dimorphic, lower submerged, longer, narrower, membranous, with short petioles; upper ones floating, petiolate, alternate or upper opposite, elliptic, lanceolate or oblong, many-nerved; stipules as long as the petiole or shorter, obtuse, scarious, caducous; spikes densely flowered, generally above the surface of water, erect, reddish brown; peduncles axillary, erect, stout or slender; spikes scapigerous, raising from a membranous spathe; flowers green, small, ebracteate; perianth segments-4, valvate; stamens with sessile anthers-4, didymous, slits extrorse; carpels-4, sessile, 1-celled, 1-ovuled, stigma subsessile, persistent; drupelets smooth, small, coriaceous or spongy, seeds 3-ribbed on the back; seed subreniform.