Fronds submerged or more usually, floating, in abundant number, solitary or in groups, oblong to ovate, asymmetrical or occasionally symmetrical, thin or spongy, 1-3 (-5)-veined, young thallus budding from the lateral pocket. Root solitary, one per frond, devoid of hairs, shortly sheathed near point of origin; sheath simple or winged laterally. Floral pocket lateral with spathe enclosing 2 staminate and one pistillate flowers, anther 4-thecous, ovary globose, ovules 1-6. Fruits 1-5-seeded. Seeds ribbed longitudinally.