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. <u>Base</u> expanded and somewhat sheathing. Base expanded and somewhat sheathing. Plants otherwise usually glabrous. <u>Margins</u> often with unicellular prickle-like hairs. Margins often with unicellular prickle-like hairs. Petiolate or sessile. <b>Stipules</b> absent. 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. <b>Calyx</b> of 3 sepals; sepals distinct. <b>Corolla</b> 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. <b>Ovary</b> inferior, (2)3–6(–20)-carpellate, 1-celled, placentation parietal, sometimes intruded; <u>ovules</u> numerous, anatropous or sometimes orthotropous; <u>styles</u> 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: