18. Coffea Linnaeus, Sp. Pl. 1: 172. 1753.
咖啡属 ka fei shu
Authors: Tao Chen & Charlotte M. Taylor
Shrubs or small trees, unarmed, often resinous on young growth; lateral branches usually spreading horizontally. Raphides absent. Leaves opposite or rarely in whorls of 3, distichous at least on lateral branches, often with foveolate and/or pilosulous domatia; stipules persistent, shortly united around stem, generally triangular, sometimes aristate. Inflorescences axillary, in each axil with 1 to several capitate to fasciculate, 1- to several-flowered cymes, these sessile to shortly pedunculate, bracteate; bracts often fused in cupulate pairs (i.e., forming a calyculus). Flowers sessile or shortly pedicellate, bisexual, monomorphic. Calyx limb obsolete or occasionally truncate or 4-6-toothed. Corolla white or pink, salverform or funnelform, inside glabrous or villous in throat; lobes 4-9, convolute in bud. Stamens 4-8, inserted in corolla throat, exserted; filaments absent or short; anthers dorsifixed near base. Ovary 2-celled, ovules 1 in each cell, attached at middle of septum; stigma 2-lobed, exserted. Fruit red, yellow, orange, blue, or black, drupaceous, globose to ellipsoid, fleshy or infrequently dry, with calyx limb when developed persistent; pyrenes 2, each 1-celled, with 1 seed, plano-convex, leathery or papery, on ventral (i.e., adaxial) face with longitudinal groove; seeds medium-sized to large, longitudinally grooved on ventral face; radicle terete, basiscopic.
About 103 species: native to tropical Africa, Madagascar, and the Mascarene Islands, several species and hybrids cultivated in moist tropical regions worldwide; five species (all introduced) in China.
Several species of Coffea are widely cultivated as a source of the drink coffee, a leading world commodity. Species limits and identifications are often difficult for wild plants, due to the complexity of the genus, its evolutionary behavior, and its numerous reduced morphological features; and the taxonomy of cultivated plants is additionally complicated by extensive, sometimes poorly documented hybridization for crop improvement during several centuries. The genus is native to Africa, Madagascar, and the Mascarenes; plants found outside this region are cultivated. Cultivated plants of Coffea generally persist after active cultivation is abandoned but do not generally establish growing permanent populations or spread. Cultivated Coffea is surveyed usefully by Purseglove (Trop. Crops: Dicot. 451-492. 1968). Coffea arabica is the most valuable species, producing highest quality coffee; this is a tetraploid species (Stoffelen et al., Opera Bot. Belg. 7: 237-248. 1996). Coffea canephora is generally the most productive species, producing a lower quality coffee; this is a diploid species (Purseglove, loc. cit.: 482-488). Coffea liberica also produces a lower quality coffee than C. arabica, is also diploid (Purseglove, loc. cit.: 488-491), and is less often cultivated. W. C. Ko (in FRPS 71(2): 22-25. 1999) additionally treated two species, C. congensis and C. stenophylla, that have been hybridized with commercial coffee (Purseglove, loc. cit.: 458) and may persist from old plantations, but these are also two names that have been widely confused in cultivation with C. arabica and C. canephora (Davis et al., Bot. J. Linn. Soc. 152: 483, 497. 2006). Some frequently used synonymous names are included here for reference.
Coffea is similar to Psilanthus J. D. Hooker, and some species have been variously treated in each genus depending on the current circumscriptions. Davis et al. (Monogr. Syst. Bot. Missouri Bot. Gard. 104: 398-420. 2005) addressed this problem and concluded by separating the genera; in their circumscription Psilanthus is not known from China. Traditional Coffea descriptions often retain characters of Psilanthus, including that of W. C. Ko (loc. cit.: 20-25). Coffea benghalensis B. Heyne ex Schultes and C. jenkinsii J. D. Hooker were included in the Fl. Xizang. (4: 445-447. 1985). Davis et al. (loc. cit. 2006: 501) treated the first of these species as P. benghalensis (B. Heyne ex Schultes) J.-F. Leroy; Purseglove (loc. cit.: 458) listed it as a native species of SE Asia and Sumatra sometimes cultivated for coffee in India. Davis et al. (loc. cit. 2006: 504) treated C. jenkinsii as a species of Nostolachma T. Durand: N. jenkinsii (J. D. Hooker) Deb & Lahiri.
The fruit of Coffea are sometimes described informally as "berries" because of their size and fleshy texture, but morphologically they are similar to other drupes of Rubiaceae; thus, this technical terminology is used here. The fruit of Coffea are also commercially sometimes called "cherries."