Leaves floating, ovate to rounded, strongly cordate, long- or short-petiolate.
Inflorescences either virtually behind the leaf or on separate peduncles, floating or emergent. Flowers of floating inflorescences submerged in bud, emergent when open. All flowers usually opening in the morning and dishevelled by afternoon, submerged when fruiting. Flowers often heterostylous with styles of 2 or 3 lengths. Corolla yellow or white [or pink], often winged or hairy on inner surface. Stigmas equal in number to placentas (2–5).
Capsule dehiscing irregularly, submerged at maturity; seeds variously smooth or sculptured.
| ||Key to the species|| |
|1||Flowers white; leaves shortly petiolate; inflorescence borne immediately behind leaf||Nymphoides indica|
|Flowers yellow; leaves long-petiolate; inflorescence separate from leaf base||2|
|2||Leaves with margins crenate; corolla lobes with a median fringed wing inside||Nymphoides crenata|
|Leaves with margins entire or rarely slightly crenate; corolla lobes without an inner wing|
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|3||Seeds strongly laterally compressed, ellipsoid, when mature shining smooth and black; robust perennial with long floating stolons and roots||Nymphoides montana|
|Seeds more or less globose or slightly compressed, straw-coloured at first but black when mature, tuberculate; smaller than Nymphoides montana, usually not producing long, floating stolons|
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