Description from Flora of China
Chomelia Linnaeus (1758), not Jacquin (1760, nom. cons.); Cupi Adanson; Webera Schreber.
Shrubs or trees, unarmed, often drying blackened. Raphides absent. Leaves opposite, sometimes with domatia; stipules persistent or occasionally tardily deciduous, interpetiolar or united around stem, triangular, often aristate. Inflorescences terminal, sometimes displaced to pseudoaxillary by subsequent growth, cymose to corymbiform, few to many flowered, sessile or pedunculate, bracteate or bracts reduced. Flowers pedicellate or sessile, bisexual, monomorphic, often fragrant. Calyx limb 5-lobed. Corolla white, pale green, or yellow, funnelform or salverform, inside glabrous or pubescent in throat; lobes 5, convolute in bud, usually strongly reflexed at anthesis. Stamens 5, inserted in corolla throat, exserted; filaments short or reduced; anthers dorsifixed. Ovary 2-celled, ovules 1 to numerous in each cell on axile placentas; stigma fusiform or linear, sulcate or striate, shortly 2-lobed at apex, exserted. Fruit baccate, leathery or thinly fleshy, globose to ellipsoid, black or perhaps sometimes white, with calyx limb deciduous; seeds several, medium-sized, plano-convex or concavo-concave, testa membranous, leathery, or crustaceous; endosperm fleshy or corneous; embryo small; cotyledon small, leaflike.
The name Chomelia Linnaeus (1758) was applied to these plants for many years; however, the later homonym Chomelia Jacquin (1760), which applies to a wholly neotropical genus, is now conserved against the Linnaean name, so the Old World plants formerly known under Chomelia are now correctly known under Tarenna.
Most of the characters that distinguish species of Tarenna are found in the corollas and calyx limb, thus specimens of Tarenna are often difficult to identify when they only have fruit from which the calyx limb has fallen. The genus was not well known in China until the work of W. C. Chen (Acta Phytotax. Sin. 22: 139-174. 1984). Tarenna apparently has secondary pollen presentation. W. C. Chen (in FRPS 71(1): 370. 1999) described the stipules as caducous, but the specimens seen all have persistent or tardily deciduous stipules. The key here closely follows that of W. C. Chen in FRPS (loc. cit. 1999: 370-372), with its emphasis on pubescence characters and number of ovules per locule, for reference. Chen (loc. cit. 1999: 370-384) considered the form (i.e., raised vs. flat vs. impressed) of the leaf midrib adaxially to be consistent within a species, but specimens studied show variation within species and overlapping among most species.
About 370 species: tropical and subtropical Africa, Asia, Madagascar, and Pacific islands; 18 species (12 endemic) in China.
(Authors: Chen Tao (陈涛); Charlotte M. Taylor)