Description

Key Characters:

Growth Form: Perennial or rarely annual herbs of fresh water or sea water, completely submerged or partly immersed, rooted in a substrate or sometimes free–floating.

Stems: Stems aerenchymatous.

Roots:

Leaves: Leaves simple. All basal or some cauline, alternate, opposite, or whorled, sometimes differentiated into blade and petiole. Base expanded and somewhat sheathing. Plants otherwise usually glabrous. Margins often with unicellular prickle-like hairs. Petiolate or sessile. Stipules absent.

Flowers: Flowers in compact cymes, especially staminate flowers, or solitary, especially pistillate flowers, inflorescences subtended by (1)2 connate or distinct bracts forming a spathe, staminate flowers often breaking loose from submerged inflorescences and floating on the surface. Flowers unisexual (and the plants dioecious or sometimes monoecious) or occasionally bisexual (perfect), actinomorphic or slightly irregular; hypanthium sometimes present. Calyx of 3 sepals; sepals distinct. Corolla of (0)3, white or variously colored, attached directly to summit of ovary or inserted on a slender hypanthium. Stamens 2–3 or sometimes numerous, in 1 to several whorls, sometimes in pairs opposite the sepals; anthers dithecal, opening by longitudinal slits, pollen grains sometimes shed and floating to the surface. Ovary inferior, (2)3–6(–20)-carpellate, 1-celled, placentation parietal, sometimes intruded; ovules numerous, anatropous or sometimes orthotropous; styles as many as carpels, each often 2–3–branched, sometimes connate at base.

Fruit: Fruit submerged; globose to linear; dry or somewhat fleshy; opening irregularly. Seeds without endosperm.

Ploidy:

Habitat:

Elevation Range: