Description: Perennial or annual aquatic herbs, often with spreading stolons.
Leaves alternate or more or less clustered at the base; petioles often with an expanded base.
Inflorescence cymose, or reduced to a few flowers, or the flowers clustered. Flowers bisexual, actinomorphic, frequently heterostylous, usually only opening for one day. Sepals 5, fused at base. Petals 4 or 5, fused at base, usually variously ornamented. Stamens as many as petals. Ovary superior or half-inferior, 1-locular with 2–5 placentas each with few to many ovules.
Fruit a regularly or irregularly dehiscing capsule; seeds with or without a caruncle and variously ornamented.
Distribution and occurrence: World: 5 genera, c. 50 species, cosmopolitan. Australia: 2 genera, c. 30 species, all States.
Angiosperm Phylogeny Website (Family: Menyanthaceae, Order: Asterales)
Text by S. W. L. Jacobs
| ||Key to the genera|| |
|1||Plants submersed with floating leaves (emergent in mudflat forms or when crowded); inflorescence lax, the flowers in pairs or umbellate, supported by 1 or more floating leaves, or erect and paniculate with > 10 flowers occurring in pairs||Nymphoides|
|Plants emergent, with erect and/or floating leaves; inflorescence erect or lax; if erect, then either capitate, paniculate with flowers arising singly (rarely paired), or consisting of less than or equal to 5 flowers; if lax, then never supported by a floating leaf||2|
|2||Each placenta with 5 to 10 ovules; inflorescence capitate, paniculate, or reduced to 5 flowers or less||Liparophyllum|
|Each placenta with 11 ovules or more; inflorescence always paniculate with > 10 flowers|
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