Flora of New Zealand Series

Bottom-rooting aquatic, annual or perennial herbs with long ± floating stolons. Lvs ± rosulate, sometimes remaining submerged and without an expanded lamina. Lvs generally alternate, sometimes subopposite below fls; petioles either long and easily distinguishable from the stems, or short and terminal and similar to stem; lamina usually floating, usually broadly ovate to orbicular and deeply cordate. Fls either 2-many in fascicles at the stolon nodes, or solitary, ephemeral, emergent; pedicels long and slender. Corolla yellow, sometimes white; lobes winged; margins prominently fimbriate. Stamens short, inserted on corolla tube. Ovary semi-inferior; style exserted or included. Capsule opening irregularly or indehiscent.

c. 20 spp., mostly in tropical and subtropical regions. Naturalised spp. 2.