Perennial herbs, submerged freshwater aquatics; thalloid base attached to substrate, foliaceous and lobed or ribbon-like and branched; stems absent or very short, to elongate and branched with leaves and flowers congested at the nodes. Leaves dissected into filiform segments. Spathellas ± sessile on the thalloid part or in clusters axillary to leaves on elongated stems, solitary or aggregated, subtended by 2 scale-like bracts, surrounding the reflexed flower bud until anthesis, when the flower breaks the spathella and the pedicel becomes exserted, with an erect flower. Flower with 2 tepals, these minute and subulate; stamen 1; ovary 1-locular, subspherical, with 2 subulate stigmas. Capsule subspherical, 8-ribbed, dehiscing into 2 equal or slightly unequal valves, the smaller one caducous; seeds many, black, flattened and ovoid.