Herbs or undershrubs. Leaves simple. Stipules absent. Flowers bisexual, actinomorphic, often in unilateral inflorescences, or subumbellate. Bracts often sheathing, dry and membranous. Bracteoles 2. Calyx tubular, gamosepalous, often conspicuously ribbed, folded, the membranous folds often hyaline, lobes 5, often scarious. Petals free, but mostly connate at the base, contorted. Disk 0. Stamens 5, epipetalous, and connate with their base. Anthers 2-celled, opening lengthwise. Ovary superior, mostly sessile, often angled, 1-celled with 1 ovule pendulous from a basal funicle; styles 5, free or variously connate; stigma subcapitate. Capsule membranous, mostly included, circumscissile near the thin base, rarely valvate from the base upwards. Seed 1, with or without endosperm, cylindric. Distr. Throughout the world, ca 10 genera.