Description

Key Characters:

Growth Form: Aquatic herbs reduced to small green bodies called fronds corresponding partly to leaf and partly to stem.

Stems: Distinct stems absent.

Roots: Roots absent.

Leaves: Leaves absent, replaced by modified stems. Fronds floating or submersed. [Turions (overwintering buds) sink to the bottom.] 1 or 2, coherent, air spaces not in tissue; reproductive cavity terminal, at base from which daughter fronds (but no flowers) originate, conic, lower side of cavity with short tract of elongated cells along median line forming connection between node and attachment to mother frond; scale at base of frond absent; anthocyanins absent; in some species pigment cells present (visible in dead fronds as brown dots); turions light green, globular, smaller than growing fronds. Cataphylls absent. Each frond globular, ovoid, or boat-shaped, 3-dimensional, smaller than 1.6 mm. Margins entire. Veins 0. Stipules absent.

Flowers: Flowers 1 per frond, originating in cavity ± on median line of upper frond surface, not surrounded by utricular scale. Flowers unisexual. Calyx (sepals) absent. Corolla (petals) absent. Stamen 1, 2-locular. Ovary superior; ovaries 1, bottle-shaped, 1-locular, tapering towards apex; style short; stigma funnel-shaped.

Fruit: Follicles: pericarp membranous; opening by bursting. Seeds 1; nearly smooth.

Ploidy: x = 10; 20; 21; 22; 23

Habitat:

Elevation Range: