Herbs perennial. Stems fleshy, usually unbranched, rarely 2- or 3-branched. Inflorescences spicate; bract 1; bractlets 2, rarely absent. Calyx tubular or campanulate, apex (4 or)5-lobed, rarely 5-parted, lobes usually equal. Corolla tubular-campanulate or funnelform, apex 5-lobed; lobes subequal. Stamens 4, inserted in corolla tube; anthers 2-celled, all fertile, usually pubescent. Ovary 1-locular, parietal placentas 4, rarely 2 or 6. Style slender, persistent; stigma 2-lobed. Capsule ovoid-globose or globose, dehiscing by 2(or 3) valves. Seeds subglobose; testa reticulate.

About 20 species: Asia, Europe; five species in China.