The genus Cinchonopsis is classified in the Tribe Cinchoneae, and includes one species of medium-sized to large trees found in wet lowland forests in the Amazon basin. Cinchonopsis can be recognized by the combination of its rather robust leaves with well developed pubescent domatia on the lower surface, its well developed, ligulate, generally obtuse stipules that are held erect and pressed together in bud and at their bases extend into a ridge that encircles the lower sides of the petioles, its terminal, lax, large inflorescences with numerous small white flowers with the corolla lobes longer than the tube, and its stiffly papery, somewhat small capsules with numerous narrow winged seeds. The flowers are shortly funnelform, densely barbate in the tube and throat, and have been reported to be monomorphic but with more collections available now appear to be distylous. The capsules are septicidal and generally open from the base, which is unusual though not unique. Cinchonopsis amazonica was previously classified in Cinchona, but based on his morphological studies of this tribe Andersson (1995) named it as a new genus; later, molecular data also supported this separation (Andersson & Antonelli, 2005).

The leaves of Cinchonopsis do not always have domatia but these are usually present, and frequently the domatia are developed not only in the axils at the junctions of the secondary veins with the midrib but also extensively along the secondary veins at the junctions of the tertiary veins. The petioles are encircled by an unusual ridge that extends from the base of the stipule on each side. This structure has not been previously mentioned, and appears to be distinctive for this genus; it is unusual, but is also found in Remijia macrocnemia and the Paleotropical genus Pagamea Aubl. The inflorescences are variously simply paniculiform from a single peduncle at the stem apex; simply panicuiform and pedunculate and produced from the stem apex and also both of the axils of the uppermost pair of leaves; or paniculiform but with the bracts of one or more pairs of secondary axes foliaceous, resembling small to nearly full-sized leaves. This last arrangement has sometimes been called axillary, but the inflorescence position is here considered terminal because the stem apices produce inflorescences not vegetative buds, and there is continuous variation in the development of the bracts vs. the foliaceous bracts so these structures are not strictly stem leaves.

Cinchonopsis is similar to Cinchona, which is found generally in premontane to montane forests in the Andes, and also ranges into very wet lowland vegetation in northwestern South America. Andersson (1995) separated these mainly by their corollas, with the tube uniform in thickness, very short, ca. 1 mm long, and shorter than the lobes in Cinchonopsis vs. with the tube uneven in thickness due to with five longitudinal thin lines in the tissue, ca. 5 mm long or longer, and always longer than the lobes in Cinchona. Andersson also separated Cinchonopsis based on its homostylous flowers, vs. distylous in Cinchona, but recent collections from Peru document distyly in Cinchonopsis. Cinchonopsis is also similar to Ladenbergia, which includes species of trees found in the same range; however Ladenbergia can be separated by its corollas with the tube well developed and longer than the lobes and its generally woody capsules that dehisce from the apex. Cinchonopsis is also similar to Macrocnemum; however Macrocnemum differs in its pink corollas with the tube well developed and longer than the lobes and its capsules with longitudinal dehiscence, with the valves remaining fused throughout and opening along sides at the septa.

Author: C.M. Taylor.
The content of this web page was last revised on 25 April 2015.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml

• Andersson, L. 1995. Tribes and genera of the Cinchoneae complex (Rubiaceae). Ann. Missouri Bot. Gard. 82(3): 409–427.
• Andersson, L. & A. Antonelli. 2005. Phylogeny of the tribe Cinchoneae (Rubiaceae), its position in Cinchonoideae, and description of a new genus, Ciliosemina. Taxon 54(1): 17–28.
• Aymard Corredor, G. A., N.L. Cuello A. & A. Fernández. 1990. Observaciones sobre el hallazgo de Cinchona amazonica Standley (Rubiaceae) en la Guayana Venezeolana. BioLlania 7: 125–130.