Description

Key Characters:

Growth Form: Glabrous, submerged perennial herbs, usually of alkaline or brackish water, sometimes in sea water, rooted in a substrate.

Stems: Stems elongating by development of axillary buds just beneath the inflorescence, the axis again terminating in an inflorescence, usually with 4 leaves between each successive inflorescence.

Roots: Fibrous root system, also rooting at nodes.

Leaves: Leaves simple. Alternate. Blades linear. Base expanded into an open sheath. Margins entire. Only the midvein evident. Sheathing. Stipules with distinct tips forming a sheath adnate to the sheath.

Flowers: Flowers usually two in short, terminal spikes, each spike initially concealed in the sheath of the uppermost leaf, peduncles eventually greatly elongating and usually becoming spirally twisted. Flowers very small and inconspicuous, bisexual (perfect). Calyx (sepals) absent. Corolla (petals) absent. Stamens 2; anthers subsessile, dithecal, opening by longitudinal slits, the relatively large pollen sacs well separated on an expanded connective. Ovary superior, carpels (2–)4(–8), distinct, each carpel becoming elevated on a slender stipe in fruit so that the carpels of each flower form an umbelliform cluster; ovule 1, pendulous, campylotropous; stigma sessile or subsessile, peltate or umbonate.

Fruit: Fruit small; drupaceous; asymmetrically ovoid; borne on the slender stipe that continually elongates as the fruit matures; the stipe often twisted. Seeds without endosperm.

Ploidy:

Habitat: Aquatic.

Elevation Range: