Perennials, caespitose, without rhizomes; often flowering in the first year (then with the slender appearance of an annual). Stem (0.5–) 1–30 cm tall, slender, erect or decumbent, rooting at the nodes, sometimes submerged or floating (floating stems to 1 m long), with a basal bulb-like swelling, and new shoots from short lower stem nodes. Leaves mostly sub-basal, terete or slightly flattened to furrowed dorsally, pluritubular, in submerged leaves bitubular to pluritubular, imperfectly or in part perfectly septate, very variable in length; auricles to c. 1.5–2.0 mm long, obtuse, membranous. Inflorescence umbelloid to (less often) anthelate, with branches usually suberect or sometimes patent to recurved, of (2–) 3–16 (–20) semiglobose to obconical heads; heads each with (2–) 3–15 flowers that often are partly replaced by proliferating shoots. Tepals (1.8–) 2–3.5 (–3.7) mm long, equal or outer ones slightly longer, ovate to lanceolate, obtuse or outer acute, green, reddish, brown or castaneous-coloured, with broad scarious margins. Stamens 3–6, 1/2–2/3 as long as tepals; anthers (0.2–) 0.3–0.8 (–1) mm long, from 1/3 as long as to equalling the filaments. Style 0.2–0.5 mm long; stigmas (0.5–) 1–1.5 mm long. Capsule (2–) 2.4–3.5 (–3.8) mm long, equalling or exceeding perianth, subcylindrical or prismatic to obovoidal or ellipsoidal, apically trigonous, obtuse or retuse, unilocular, green to light or dark brown. Seeds ±ovoid, 0.4–0.6 mm long, apiculate, pale brown, c. 25-striate, reticulate. 2n = 40, fide S.Snogerup, Bot. Not. 113: 246 (1960); M.Zandee, Proc. Kon. Ned. Akad. Wetensch., C, 84: 245 (1981). Fig. 84.