Annual, floating herbs; stem long, flexuous, rooted in mud; petiole slender, woolly very long, about 10-15 cm, with a spongy dilatation near the apex; leaves stipulate, dimorphic; submerged opposite, pinnatipartite with filiform segments; floating ones arranged in rosette, crowded in the upper part of stem, lamina rhomboidal or wedge shaped, posterior margin entire, anterior crenate, densely villous beneath, upper surface glabrous; flowers solitary, axillary, peduncled; calyx tube short, limbs 4, persistent, 2 become spinescent in fruit; petals-4, white, small; stamens 4; ovary half inferior, 2-celled, style subulate, stigma capitate, ovule solitary, pendulous; fruit large, bony, 1-celled with 4 angles, 2lined by spines of persistent calyx, other two angles sometimes obsolete; seed 1 with inequal cotyledons.