Description from Flora of China
Castanola trinervis Llanos, Mem. Real Acad. Ci. Exact. Madrid, 2: 503. 1859; Agelaea cambodiana Pierre; A. wallichii J. D. Hooker; Castanola glabrifolia Schellenberg; C. obliqua Schellenberg.
Lianas or climbing shrubs. Stems ca. 5 cm thick; branchlets hairy when young, glabrous when mature. Leaves 3-foliolate; petiole 2.5–7 cm; petiolules glabrous, lateral ones ca. 1 cm; terminal leaflet blade ovate or elliptic, 6–10 × 3–4.5 cm, base subrounded, apex acuminate; lateral leaflet blades ovate, 5–7 × 2–4 cm, base rounded and slightly asymmetric; all leaflet blades leathery, initially minutely tomentose abaxially, later glabrescent, glabrous adaxially, lateral veins 4–6-paired, usually with 1 pair at base (so base appearing 3-veined), all veins slightly prominent abaxially. Panicles axillary, dense, 2–3(–6) cm; rachis and pedicels grayish tomentose. Flowers 4–6 mm in diam., fragrant. Sepals ovate-lanceolate, 1.3–2 mm, softly gray hairy abaxially. Petals white, oblong-oblanceolate, 4–5 mm, glabrous. Stamens ca. 10, glabrous. Carpels 4 or 5; ovary hirsute. Style glabrous. Follicles few, obliquely obovoid, 1–2.5 × 0.5–1.2 cm, densely minutely tomentose, base slightly narrowed, apex obtuse and shortly beaked; pericarp rugulose or warty. Seed black, oblong or oblong-ovoid; aril yellow, covering 1/3–3/4 or more of seed surface.
Sparse forests. Hainan [Cambodia, Indonesia, Laos, Malaysia, Philippines, Thailand, Vietnam].