Prostrate or ascending annual herb, (3-) 8-35 cm, much-branched from the base and in well-grown specimens frequently also above. Stems slender, ± angular or sulcate, yellowish-green to reddish, glabrous or occasionally shortly papillate. Leaves glabrous, linear-oblong to linear-oblanceolate, 8-32 x 2-5 mm, long-attenuate at the base into a slender petiole of variable length, the apex rounded to distinctly emarginate, mucronulate. Flowers green, all in axillary cymose clusters up to c. 8 mm in diameter; male and female flowers intermixed or the males mostly towards the top of the cymes. Bracts and bracteoles narrowly oblong-elliptic with a green central vitta and broad hyaline margins, 0.75-1 mm, obtuse. Perianth segments 2, one frequently smaller than the other, 0.75-1 mm, similar to the bracteoles, often concave-subcucullate at the apex; stamens of male flowers also 2. Stigmas 2, very short and highly papillose. Capsule ellipsoid, slightly compressed, c. 1.25 mm, delicate and hyaline, indehiscent, rupturing between the 4-5 strong, raised longitudinal ribs, the fifth rib when (as usually) present set close to one of the four main ribs. Seeds clearly visible through the capsule, c. 0.8 mm, round, compressed, almost smooth, shining with slightly duller margins.