Submerged, slenderly branched
brackish-water plants. Leaves elongate, filiform with stipule-like sheaths.
Flowers minute, bisexual, 2-6 together within a leaf-sheath, on an ultimately
elongating, straight or spirally twisted peduncle. Perianth absent. Stamens 2,
anthers sessile, opposite, 2-celled. Carpels 4, 1-ovuled, ovule pendulous,
stigmas sessile. Fruits of 4 stipitate, ovoid, obtuse or beaked achenes. Seeds
uncinate, embryo straight, endosperm absent.