Glabrous annual, 5-50 cm., many- or few-stemmed. Stems decumbent to erect, sometimes reddish. Leaves 1-12 x 1-7 cm., petiolate, ovate to oblong, entire, truncate to cordate at base, more or less rounded and apiculate at apex. Staminate flowers 1.5-2 mm., on filiform pedicels together with some perfect ones, clustered at upper part of interrupted racemes. Pistillate flowers 1.5 mm., sessile or nearly so, clustered at nodes and lower parts of racemes; perianth urn-shaped, greenish-red, much growing in fruit, with outer segments spinescent, more or less recurved at apex and inner ones ovate-triangular, 3-ribbed. Achene about 4 mm., enclosed in perianth, triquetrous. Fruits of two kinds, aerial and subterranean, the latter crowded near root neck, larger and less spinescent than the former. Fl. December-May.
Var. spinosa. Leaves many, up to 12 x 6.5 cm.; petiole generally as long as or shorter than blade. Fruit 6-8 mm., more or less spinescent. Cotyledond more or less wide, club-shaped.