Aquatic, annual or perennial
herbs, free-floating or rooted in the substrate. Young leaves linear and
submerged, mature leaves ovate to cordate. Inflorescence an involucrate cymose
umbel or a solitary flower. Flowers bisexual, regular, hypogynous, trimerous.
Perianth 6, sepals 3, green, persistent,
petals 3, alternating with sepals, white or yellow, deciduous. Stamens
6-9 or numerous, staminodes occasionally persistent. Carpels 3 to numerous,
free, in a single or rarely 2 whorls,
lateral surface of carpels nectariferous towards base, ovules numerous,
scattered inside the carpel wall, anatropous to more or less campylotropous.
Fruit of distinct follicles, opening by adaxial suture. Seeds numerous, embryo