Submerged, tufted, dioecious, stoloniferous herbs, variable in size; rooting in mud; leaves, radical or crowded at the basse, linear, very long about 40cm, shorter according to the depth of water-body, entire or serrulate at the tips, 3-9 nerved, sheathing at base; male flowers numerous, minute, on 3 lobed, shortly stalked spathes; when ready to open detached and float on water with expanded perianth, pedicels long, slender; sepals 3, ovate-oblong, petal absent; stamens 1-3, anthers, didymous, pistillode absent; female flowers solitary in a tubular, 3-toothed spathe terminating in a long, spiral, filiform scape the uncoiling of which brings the flowers to the surface to get fertilized by the floating males and again coils to bring the ovary down to ripen under water; perianth as in males; staminodes 3, each 2 fid; ovary narrow, not produced upwards, ovules numerous; styles 3, splitted into broad, notched stigmatic lobes; fruits linear, 5-7 cm long, included in the spathe; seeds numerous, oblong.