Erect, perennial herbs. Leaves petiolate, polymorphic, aerial leaves lanceolate to elliptic-ovate, with sagittate base, submerged leaves modified into ribbon like phyllodes, acute. Inflorescence an erect raceme of 3-flowered verticils, each verticil subtended by 3 subconnate bracts. Flowers unisexual (plants then monoecious or dioecious) or polygamous, male flowers present towards apex of racemes, female or bisexual flowers towards the base, pedicels erect or suberect, recurved & thickened in fruit. Thalamus globular or oblong. Sepals recurved, patent or appressed persistent in fruit. Petals white, occasionally pink or purple-spotted at the base. Stamens 6-many, staminodes mostly present in female flowers. Carpels numerous, spirally borne on the thalamus; ovaries laterally compressed, uniovulate; styles erect, terminal or lateral, stigma papillate. Achenes many, laterally compressed, thin, winged and beaked.