Trigonostemon sinclairii Jabl.

Yu, R. - Y. & Welzen, P. C. van, 2018, A taxonomic revision of Trigonostemon (Euphorbiaceae) in Malesia, Blumea 62 (3), pp. 179-229 : 212

28. Trigonostemon sinclairii Jabl. — Map 10

Trigonostemon sinclairii Jabl. (1963) 154, f. 3, 4; Whitmore (1973) 135. — Type: SFN (Sinclair & Kiah bin Salleh ) 40418 (holo SING), Malaya, Terengganu, Block 3B Gunong Tebu F.R., 51st mile Kuala Terengganu – Berut Road .

Shrubs or small trees, up to 5 m tall, stem sparsely branched, flowering branches 0.8–1.3 mm diam. Indumentum often of 2 layers of simple hairs, shortly villose and longer papillate-hispid. Outer bark 0.1–0.2 mm thick, often fissured, yellowish to brownish, villose and papillate-hispid; inner bark c. 0.5 mm thick, fibrous, dark brownish to blackish, with sap; sapwood 0.2–0.3 mm thick, yellowish to reddish brown; heartwood 0.4–0.7 mm diam, brownish. Stipules subulate, c. 1 mm long, caducous, often not seen. Leaves: petiole 4–15 cm long, villose and hispid; blade oblong, 20–45 by 8–17 cm, coriaceous, base obtuse or slightly cordate, with 2 adaxial glands, latter falcate or subulate, but often covered by long hairs, margin entire, often papilloseciliate, apex acute to acuminate, or sometime rounded, both sides papillate-hispid; midrib raised and densely villose and hispid on both sides, nerves 15–20 pairs, slightly raised on both sides, curved and narrowed near margin, with two layers of hairs, villose and papillate-hispid, veins scalariform, papillate-hispid (only one layer, not villose), veinlets reticulate, obscure above. Inflorescences: staminate ones axillary, raceme-like thyrses, rachis up to 25 cm long, densely villose but sparsely hispid; bracts linear, 6–12 by 0.7–1 mm, hispid; pistillate inflorescences axillary, racemose, or sometimes sparsely branched at bottom, rachis sometimes hollow, up to 40 cm long, villose and hispid; bracts as staminate inflorescences, but larger, up to 20 by 2 mm. Staminate flowers c. 7 mm diam; pedicel 0.5–0.8 mm long, 0.2–0.4 mm diam, sparsely hispid; sepals lanceolate, 1.5–2 by 1–1.5 mm, apex acute, outside hispid and with a gland near apex, inside glabrous, sometimes with a few pale pustules on both sides; petals elliptic, c. 4.8 by 2.5 mm, base rounded, apex acute to rounded, dark reddish, contort, glabrous to often with sparsely pale pustules on both sides; disc glands rhomboid, 0.5–0.7 by 0.4–0.65 mm and c. 0.2 mm thick, apex acute, occasionally with sparsely pale pustules; stamens 3, androphore erect, c. 0.6 mm long, anthers ellipsoid, gathered on the top of androphore, 0.5–0.6 mm long, connectives with numerous apical pustules or droplets with secretion. Pistillate flowers (fruiting) 1–2 cm diam; pedicel 1–1.2 cm long, c. 1 mm diam, villose and sparsely hispid; sepals triangular, already enlarging, c. 2 by 1 cm, finally leaf-like, persistent, margin with few teeth near top, apex acuminate, both sides hispid and often villose or ciliate along veins and margins; petals not seen, caducous; disc lobes semi-orbicular, c. 0.4 by 0.7 mm; ovary densely hispid, styles c. 0.5 mm long, stigmas completely bifid, arms c. 0.8 mm long, bent. Fruits c. 1.5 cm diam, hispid outside; wall c. 0.6 mm thick, exocarp not splitting off; columella c. 6.5 mm long. Seeds c. 6.5 mm diam, often with sparse pustules on surface; hilum elliptic, c. 4 by 2 mm, apex often apiculate.

Distribution — Malay Peninsula (endemic).

Habitat & Ecology — Primary forest to newly logged forest on hill side. Flowering: May and August; fruiting: July and September.

Note — An extremely hairy species with large accrescent pistillate sepals.