Shrub, or less often a tree to 22 m high and 50 cm ø. Twigs sparsely pilose, puberulous, or appressedly pubescent, glabrescent, often zigzag. Leaves alternately or (on the leaders) spirally arranged, glabrous above, sparsely appressedly fine-hairy beneath, rarely patently hirsute, especially on midrib and nerves and towards the margin, (narrowly) elliptic or sometimes ovate, acuminate to caudate with acute to rounded base, 5-13(—18) by 2-4½ (-6)cm; nerves (4-)6-8(-ll) pairs, meeting in a looped intramarginal vein; petiole 2-8 mm. Flowers in a fascicle of reduced, often branched, racemes to 2½ cm long. Bracts and bracteoles persistent, minute (rarely to 3 mm), as the axis pubescent; often several bracts present, indicating the origin from a more branched inflorescence. Pedicel 1-5 mm, pubescent. Calyx divided into (4-)5(-6) broadly ovoid, rounded, appressedly pubescent or glabrous lobes, c. 1 mm long but sometimes the lobes different in size, often some of the lobes petaloid. Corolla glabrous or more often with minute hairs towards the outer base, rarely some hairs on the back too, 2-4½ mm. Stamens 12-35. Disk glabrous to more or less pilose, low annular. Ovary appressedly hairy, c. 1 mm high; style hairy, especially towards the thickened base, rarely glabrous, 2-3½ mm. Fruit broadly or narrowly ampulliform, often curved, the belly globose or ovoid, the neck broadly conical, dark violet-blue or cobalt-blue, 5-7 by 3-5 mm; stone brain-like grooved without or with c. 10 shallow grooves. Seed 1, much lobed, with slightly curved embryo.
In primary high and open secondary forest and thickets, common in disturbed forest, rather indifferent to soils, besides on latosols, recorded from sand (Banka), in Borneo from sandstone, black soils, seasonally swampy land and Dipterocarp forest, also riparian, in Udjong Kulon from raised coral limestone, from sea-level up to c. 2200 m. Fl. June-Sept. (Nov.-April); fr. Sept.-March. Several times flowers are noted to be scented, but once recorded as emitting a pervasive sour smell (Malaya, WHITMORE).
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Primary high, and open secondary forest and thickets, common in disturbed forest; it is found in a wide range of soils and Dipterocarp forest, also riparian, at elevations from sea-level up to 2,200 metres.