Description from Flora of China
Kinkina Adanson; Quinquina Boehmer.
Shrubs or usually trees, unarmed; buds flattened with stipules erect and pressed together; bark usually notably bitter. Raphides absent. Leaves opposite, decussate, usually with well-developed domatia; stipules caducous, interpetiolar or shortly united around stem, ligulate to obovate, entire. Inflorescences terminal and often also in axils of uppermost leaves, cymose to paniculiform, many flowered, pedunculate, bracteate. Flowers pedicellate, bisexual, fragrant, usually distylous. Calyx limb 5-lobed. Corolla yellow, pink, purple, red, or occasionally white, salverform or funnelform, inside glabrous or pubescent in throat, with tube often weakly 5-ridged outside; lobes 5, valvate in bud, with margins densely ciliate to villous. Stamens 5, inserted in corolla tube, included to partially exserted; filaments short to developed, glabrous; anthers dorsifixed. Ovary 2-celled, ovules many in each cell on axile placentas; stigma 2-lobed, lobes capitate to linear. Fruit capsular, ovoid to cylindrical or ellipsoid, septicidally dehiscent into 2 valves from base or sometimes from apex with valves then loculicidal through septum, stiffly papery to woody, often lenticellate, with calyx limb persistent; seeds numerous, medium-sized, ellipsoid to fusiform and somewhat flattened with membranous marginal wing and elliptic central seed portion; endosperm fleshy; cotyledons ovate.
Several species of Cinchona are the natural source of quinine, which has long been used worldwide as a treatment for malaria. Quinine is found along with several other alkaloids in high concentrations in some species of Cinchona, particularly the bark; these alkaloids give the plants their bitter taste. Cinchona is native to South America, where its species are not all well differentiated, are morphologically variable, and hybridize freely especially in cultivation, where numerous artificial hybrids have been created. Cinchona was recently monographed by Andersson (Mem. New York Bot. Gard. 80: 1-75. 1998), followed here, who clarified the identities of the commonly cultivated species.
Cinchona officinalis (Linnaeus, Sp. Pl. 1: 172. 1753; 正鸡纳树 zheng ji na shu) is native to South America (Ecuador) and perhaps occasionally cultivated in tropical regions worldwide. No confirmed documentation of this species has been seen from China. The name has long been incorrectly used in cultivation for plants treated here as Cinchona calisaya (Andersson, loc. cit.: 55-57). It is included for reference in the key to species.
Twenty-three species: Central America (Costa Rica, Panama) and South America (Bolivia, Colombia, Ecuador, Peru, Venezuela) and cultivated as species and hybrids in tropical regions worldwide; two species (both introduced) in China.
(Authors: Chen Tao (陈涛); Charlotte M. Taylor)