Description from Flora of China
Herbs, rarely subshrubs or shrubs. Roots fibrous. Stems usually erect. Leaves opposite, rarely 3-verticillate, petiolate, pinnately compound, rarely simple or pinnately lobed (or simple and bearing bulbils along margin). Inflorescences terminal, cymose, many flowered. Flowers bisexual, usually pendulous, 4-merous, brightly colored, large. Calyx tubular or rarely campanulate; tube sometimes basally dilated. Corolla purple-red (in China), tubular to salverform, equaling or longer than calyx; lobes shorter than or scarcely longer than tube. Stamens 2 × as many as petals, inserted below middle of corolla tube, usually near base; filaments equaling corolla tube. Nectar scales entire or emarginate. Carpels erect, free. Styles long. Follicles many seeded.
About 20 species: Africa (including Madagascar); one species (introduced) in China.
(Authors: Fu Kunjun (Fu Kun-tsun); Michael G. Gilbert)