Annual herbs. Stems rigid, branched. Leaves opposite, fleshy, terete-linear; stipules scarious. Heads 4-7-flowered, spherical, becoming detached from plant when ripe together with the short, jointed peduncle. Floral leaves united with flowers, indurated, spiny in fruit. Calyx cup-shaped at base, adnate to bracts; lobes 5, hooded and sub-spinescent. Petals O. Stamens 2-5, short, inserted at the discoid margin of calyx tube. Ovary adnate at base to calyx tube, free above, 1-celled, 1-ovuled; ovule suspended from basal funicle; style 2-fid into 2 somewhat recurved stigmas. Urticle membranous, adnate to calyx tube, irregularly lacerate at apex. Seeds somewhat compressed, ovoid, with annular embryo.