Vleisia Toml. & Posl.: 273 (1976).
Submerged annuals with slender rhizomes. Stems upright, usually unbranched. Leaves alternate, leaf blade flattened, linear up to 100 mm long and 2 mm wide, with submarginal fibrous strands and submarginal veins connected to midvein by obliquely extended commissures; sheathing base auriculate. Male flowers single, naked; stamen with 8 microsporangia, connective terminating in a blunt appendage and with two vestigial outgrowths opposite each other on connective, hidden by anther lobes at maturity. Female flowers borne in a tubular sheath; carpel solitary; style lengthens rapidly during anthesis and displays a large, ephemeral, obliquely funnel-shaped stigma. Fruit an asymmetrical, warty, bean-shaped drupelet.
Species 1: Pseudalthenia aschersoniana (Graebn.) Hartog, endemic to the W Western Cape; in brackish, coastal pools near Lamberts Bay and south to the Cape Peninsula.