Shrubs or straggling to twining climbers. Leaves opposite, rarely verticillate; stipules reduced to an interpetiolar line; leaf blade margin entire. Thyrses axillary and terminal, many-flowered or fascicles with few flowers to 1-flowered. Flowers 5-merous. Sepals imbricate. Corolla funnelform; lobes imbricate. Stamens inserted at base to middle of corolla tube; filaments strap-shaped to filiform; anthers narrowly ovate to narrowly oblong, included to exserted, 2-locular, base sagittate. Ovary 2-locular, with several ovules per locule. Style filiform; stigma 4-cleft. Capsules ovoid to narrowly ellipsoid, septicidal, 4-valvate, several-seeded. Seeds winged.

Three species: two in North America, one in E and SE Asia; one species in China.