Annuals or short-lived herbs with branches erect or decumbent, to 6 cm long, often rooting at nodes, usually forming dense cushions. Leaves linear-lanceolate, 1.5–4.2 mm long, 0.3–0.6 mm wide, acute, more or less biconvex; sheath 0.4–0.8 mm long. Flowers solitary in axil of 1 leaf at usually 2 or more successive nodes; 4-merous; calyx-lobes broadly triangular, 0.2–0.7 mm long, rounded to (rarely) acute; corolla white, lobes oblong-oblanceolate, 0.9–1.6 mm long, obtuse or rounded, erect; nectary scales narrowly oblong, 0.3–0.5 mm long, c. 0.1 mm wide, rounded or truncate; carpels cylindric-ovoid, with 8–14 ovules. Follicles opening along the whole suture; fruiting pedicel usually elongating, 0.4–13 mm long; seeds 0.3–0.35 mm long, with several longitudinal ridges more or less granulate to tuberculate. Flowers mainly Aug.–Nov.