Description from Flora of China
Herbs, shrubs, or small trees; pubescence of simple and glandular hairs. Leaves petiolate or sessile, entire or subentire. Inflorescences paniculate, racemose, or reduced to solitary flowers; peduncle mostly erect; bracts mostly present. Flowers sometimes showy, mostly fragrant, zygomorphic, 4- or 5-merous, pedicellate. Calyx regular or irregular, tubular or tubular-campanulate, lobed. Corolla tubular, funnelform, or salverform; tube lobed to subentire. Stamens inserted below middle of corolla tube; filaments slender; anthers dehiscing longitudinally. Disc ringlike, nectariferous. Ovary 2-locular. Stigma 2-lobed. Fruiting calyx persistent, slightly inflated, partially or completely enveloping fruit. Fruit a dry capsule dehiscing by apical valves. Seeds numerous, minute; embryo erect or slightly bent; cotyledons linear.
About 95 species: Africa, Americas, Australia, and Oceania; three species are cultivated in China as drug plants or as ornamentals, at least one is naturalized.