Soft aquatic or semi-aquatic herb, the creeping and rooting stems giving off ∞ erect, us. simple, branches up to c. 10 cm. tall. Lvs opp., obovate, entire, obtuse, almost fleshy, c. 2 × 0·5 mm. Fls solitary in the axils of the upper lvs, each subtended by two linear to triangular bracteoles, unisexual; ♀ lower, sessile, lacking sepals, petals and stamens; ovary c. 0.6 mm. long, styles 4, divergent, stigmas plumose; ♂ uppermost, 2-4, the undeveloped ovary forming a short pedicel; sepals 0, petals 4, dark red, c. 2.5 mm. long, reflexed after anthesis; stamens 8; fr. dark red, c. 1 mm. long, deeply divided into 4 rounded mericarps, not tapered above, surface slightly rough.

2n = c. 21

Dioecious perennial terrestrial herb, stems prostrate (rarely erect, forming tight cushions to 7 cm high), branching freely, rooting at nodes, forming clumps to 10 cm in diameter, glabrous. Leaves all opposite, entire, obovoid, 1.8-3.5 mm long, (0.5-)0.7-1.1 mm wide, ± planar or slightly concave on upper surface, convex below, spreading or slightly upward-curving, glabrous.. Hydathodes absent. Rarely, in inundated plants, submerged leaves are formed, which are linear, 2 mm long, 0.2 mm wide. Inflorescence a terminal spike with the unisexual flowers borne in the axils of opposite upper leaves indistinguishable from lower (sterile) leaves. Male and female flowers apparently borne on separate plants. Bracteoles linear, 0.5-0.7 mm long, 0.1-0.2 mm wide. Hydathodes 0. Male flowers 4-merous, sessile, usually in axils of the uppermost pair of leaves only. Sepals 0. Petals 4, green at first, becoming white with a dark reddish spot at tip (rarely, completely dark red), hooded, non-unguiculate, 1.5-1.8 mm long, 0.7-1.0 mm wide, reflexed at anthesis. Stamens 8; filaments 0.2-0.3 mm long, elongating to 0.8-11.0 mm at anthesis; anthers yellow, oblong, 1.2-1.3 mm long, 0.4 mm wide, 4-celled, nonapiculate or very weakly apiculate. Styles 0. Ovary vestigial. Female flowers 4-merous, sessile, in axils of upper 4-8 pairs of leaves. Sepals, petals and stamens 0. Styles 4, ± sessile, stigmas white, fimbriate, capitate. Ovary green, shortly cylindrical, 0.8 mm long, 0.6-0.8 mm wide, longitudinally channelled between styles, rounded opposite styles, otherwise smooth. Fruit black, depressed-globular, 0.9-1.0 mm long, 1.1-1.4 mm diameter, suture between mericarps buff coloured; mericarps separating at maturity. Mericarps planar on inner faces, outer face convex, smooth or very weakly punctate, sometimes with a faint median longitudinal ridge.

Dioecious perennial herb; stems usually prostrate, rarely erect, forming often patches or tight cushions to 7 cm high, branching freely, rooting at nodes, forming clumps to 10 cm diam. Lvs monomorphic, opposite, entire, obovoid or nearly so, 1.8-3.5 × (0.5)-0.7-1.1 mm, ± flat or slightly concave on upper surface, convex below, spreading or slightly upward-curving. Submerged lvs present. Fls in the axils of upper lvs; fertile lvs similar to lower lvs. Bracteoles linear, 0.5-0.7 × 0.1-0.2 mm. ♂ fls sessile, usually in axils of the uppermost pair of lvs only; sepals 0; petals 4, with reddish spot at tip, rarely completely dark red, hooded, 1.5-1.8 × 0.7-1 mm. ♀ fls sessile, in axils of upper 4-8 pairs of lvs; sepals, petals and stamens 0. Frs 0.9-1 × 1.1-1.4 mm diam., depressed-globular, smooth or weakly punctate on dorsal surface of mericarps.