Floating or creeping, aquatic, perennial
herbs. Leaves alternate, often subopposite, cordate, elliptic or ovate, entire.
Flowers white or yellow, clustered at the nodes of peduncle. Sepals 5 or 4.
Petals 5 or 4, ciliate, fimbriate or with longitudinal fold down their middle.
Stamens 5 or 4, epipetalous. Ovary superior, 1-celled, stigmas 2-lobed.
Capsules ellipsoid, ovoid or globose, subindehiscent. Seeds many, discoid,
tuberculate, reticulate or smooth, rarely winged.