Description from Flora of China
Shrubs parasitic, most young parts usually with dense stellate and/or verticillate hairs, rarely glabrous (in T. delavayi). Leaves opposite or alternate, pinnately veined. Inflorescences axillary, umbels or rarely short, irregular racemes, 2-5-flowered; 1 bract subtending each flower, usually scale-like. Flowers bisexual, 4[or 5]-merous, zygomorphic. Calyx ellipsoid or ovoid, rarely subglobose, base not attenuate, limb annular, entire or denticulate, persistent. Mature flower bud tubular, tip ellipsoid or ovoid. Corolla sympetalous, slightly curved, basal portion ± inflated, split along 1 side at anthesis, lobes all reflexed toward the side away from the split. Stamens inserted at base of corolla lobes; filaments short to almost absent; anthers 4-loculed, sometimes multilocellate. Pollen grain trilobate or semilobate in polar view. Ovary 1-loculed; placentation basal. Style filiform, 4- or 5-angled; stigma usually capitate. Berry ellipsoid or ovoid, rarely globose, exocarp leathery, verrucose or granular, rarely smooth, pubescent or glabrous, base rounded.
About 25 species: S and SE Asia; 18 species (nine endemic) in China.