or rarely annual, partially or completely submerged aquatic herbs, rarely
floating, of fresh- or salt-water habitats, rooted to the substrate or
sometimes free floating. Leaves basal, and often crowded, or cauline, usually
sessile, linear or orbicular, with or without petioles, often more or less
sheathing. Inflorescence a compact, usually few-flowered cyme in especially
staminate flowers, or a single flower in pistillate flowers, collectively
subtended by a bifid spathaceous bract. Flowers bisexual or more commonly
unisexual, small and inconspicuous, actinomorphic or slightly irregular.
Perianth commonly of 3 distinct, green sepals and 3 distinct white or coloured
petals. Male flowers with stamens 3- many, anthers 2-celled, 1 or more
rudimentary sterile ovaries (pistillodes) usually present, female flowers
unipistillate, ovary inferior, unilocular, often with more or less partial
partitions, style 1, usually divided into as many branches as placentae, ovules
numerous on each placenta, anatropous or seldom orthotropous. Fruit berry-like,
globose or linear, dry or fleshy, indehiscent, submerged. Seeds several to
numerous, embryo straight.