or marshy herbs, annual or perennial. Roots fibrous from stout rhizomes. Leaves
floating or emerged, basal, long pedicelled, blades linear to ovate or
sagittate or hastate, reticulately veined. Inflorescence a raceme or panicle.
Flowers bisexual or unisexual, pedicelled, often in whorls, bracteate. Perianth
segments 6 in two series, outer 3 green and sepaloid, inner 3 petaloid,
persistent. Stamens 6 or more, rarely 3, hypogynous, anthers 2-celled,
basifixed or versatile. Carpels 2 to many. Ovary superior, unilocular, ovule
solitary. Fruit an achene, rarely follicular. Seeds oblong or horse-shoe