Subshrubs, perennial, or annual herbs. Raphides present. Leaves opposite, usually with leaflike stipules in whorls of 4-14, sessile to shortly petiolate, without domatia; leaflike stipules rarely reduced. Inflorescences thyrsoid, paniculiform to capitate, with terminal and often also axillary pedunculate to sessile cymes, bracteate with bracts often fused and sometimes involucral. Flowers pedicellate to sessile, with prophylls, bisexual, monomorphic. Calyx limb reduced, practically absent. Corolla blue, pink, purple, or yellow to greenish or white, salverform, funnelform, campanulate, or sometimes rotate, glabrous inside; lobes 4 or 5, valvate in bud. Stamens 4 or 5, inserted in corolla tube, exserted (or sometimes included); filaments developed to short; anthers dorsifixed. Ovary inferior (hypanthium), 2-celled, ovules 1 in each cell, erect and axile; stigma globose to clavate, often 2-lobed, included or exserted. Fruit schizocarpous, generally didymous, dry; mericarps 2, indehiscent, with 1 seed, subglobose, ellipsoid-oblong, or reniform, smooth to tuberculate, glabrous to pubescent (but never with uncinate hairs); seeds small, with membranous testa; endosperm corneous; embryo curved; cotyledons leaflike; radicle terete, hypogynous.