Habit: aquatic herbs
Leaves: basal or submerged in water often bladeless; if emergent often with expanded blades
Flowers: whorled, umbellate, thyrsoid
Sepals: 3
Petals***: 3 ***often petaloid
Stamens: 6-many
Gynoecium***: ***apocarpous, of many carpels; all superior with 1 ovule
Fruit: an aggregate of achenes
Diversity: 1 genera/96 species
Distribution: cosmopolitan; most north temperate areas
Economics: aquarium plants...