Trees or shrubs, dioecious [or sometimes polygamo-dioecious], unarmed, terrestrial [or sometimes epiphytic]. Raphides absent. Leaves opposite or verticillate, usually with domatia, notably leathery [to papery or succulent]; tertiary venation finely lineolate [or sometimes not visible]; stipules caducous, interpetiolar [or calyptrate], triangular. Inflorescences axillary, cymose with axes dichotomous to scorpioid, few to several flowered with pistillate usually fewer flowered than staminate, pedunculate, bracteate or bracts reduced; bracteoles sometimes fused in pairs. Flowers sessile, unisexual. Calyx limb cupular, truncate to 4- or 5-lobed. Corolla white to pale yellow, funnelform or tubular-funnelform with pistillate frequently shorter and broader in diam. than staminate, outside densely strigose to sericeous, inside glabrous, leathery; lobes 4(-10), thinly imbricate in bud (i.e., "subimbricate" of Darwin 1993, with margins thinly overlapping; see comment below). Stamens 4(-10), inserted in corolla throat, exserted; filaments short; anthers dorsifixed, at base 2-lobed. Ovary many celled, ovules 1 in each cell, pendulous from apical placentas; disk hirsute; style 4-12-parted with segments linear, often unequal; stigmas 4-12 (i.e., 1 on each style arm), papillose, included or exserted. Fruit red or black, drupaceous, thinly fleshy, ovoid, subglobose, or oblate (i.e., depressed globose), often 4- or 5-ridged when dry, with calyx limb persistent; pyrenes several to numerous [to 350 or more], 1-celled with 1 seed, narrowly oblong to cylindrical, bony; seeds cylindrical, straight or curved; testa membranous; endosperm scanty or absent; embryo straight or curved; cotyledons minute, flattened; radicle elongate, terete, ascending.

Darwin (Allertonia 7(1): 1-39. 1993) noted that although the corolla lobes have been commonly described as valvate in Timonius, in fact, they are "subimbricate" with the margins only thinly overlapping; this arrangement is here called "thinly imbricate." A notable characteristic of Timonius within the Rubiaceae is the multiplication of ovules, or often entire files of ovules, as well as the number of cells in the ovary, from the 2 cells that are typical of most Rubiaceae, to far past the 5-9 cells found in Guettarda. Darwin (loc. cit.; Syst. Bot. Monogr. 42: 1-86. 1994) has monographed part but far from all of this large genus.

About 150-180 species: tropical SE Asia and the Pacific islands; one species in China.

(Authors: Chen Tao (陈涛); Charlotte M. Taylor)