Annual herbs covered with long, +/- appressed yellowish hairs; stem erect, usually much branched from base. Leaves elliptic to elliptic-lanceolate, petiolate; stipules 0. Flowers solitary in axils of upper, very closely arranged leaves, heterostylous. Sepals hyaline-membranous, connate in lower half. Petals and stamens adnate to base of calyx tube, falling off with calyx and stamens after pollination. Stamens: filaments linear, flattened below; anthers cordate-ovate. Ovary ovoid, with 3 parietal placentas; styles 3, filiform, straight, with laciniate-flabellate stigmas. Capsule 3-valved, opening loculicidally from apex. Seeds oblong-obovoid, curved, with rigid, reticulate-alveolate testa; aril entire; albumen abundant, oily.
Monotypic genus from Madagascar, SE and E Africa: Hyalocalyx setifer Rolfe; sthn trop. Afr.: Mozambique.