Trigonostemon flavidus Gagnep.

Yu, R. - Y. & Welzen, P. C. van, 2018, A taxonomic revision of Trigonostemon (Euphorbiaceae) in Malesia, Blumea 62 (3), pp. 179-229 : 195

11. Trigonostemon flavidus Gagnep. — Map 4

Trigonostemon flavidus Gagnep. (1922) 749; (1925b) 320; P. T. Li & M.G. Gilbert (2008) 273. — Type: Harmand 3273 (holo P), Laos, in Lakhon mountains , near Me-Kong .

Trigonostemon heterophyllus Merr. (1930) 38; H.S. Kiu (1996) 163; Chantar. (2005) 24; (2007) 577, pl. 31: 1. — Type: W. T. Tsang 594 (= LU ( Lingnan University ) 17343) (A*, B*, BM, BO, ECON*, G*, K, L, MO*, NTUF*, NY*, P, PE, US, WIS*), China, Hainan, Danzhou County ( Taam Chau District ), Mt Sha Bao ( Sha Po Shan ).

Evergreen, small trees, 1–2.5 m tall; flowering branches up to 4 mm diam, grey, densely hirsute. Bark c. 0.3 mm thick, smooth or roughened; wood reddish brown. Stipules subulate, c. 0.7 mm long, hirsute around base. Leaves: petiole terete but sometimes flattened or grooved above, 0.2–1.2 cm long, densely hirsute; blade obovate or oblanceolate, sometimes unequal, unevenly narrowed in the lower middle part, 9–35 by 5–9 cm, thin chartaceous or membranous, base abruptly rounded, with 2 adaxial glands, margin distantly serrate, teeth small and nipple-like, apex caudate to acuminate, dark green above and dull light green underneath, hirsute on both sides, especially on nerves and margin; midrib thin, elevated on both sides, nerves 10–12 pairs, veins reticulate, often obscure. Inflorescences bisexual, cauline, usually in short cymes or thyrses, 1–3 cm long, hirsute, often bracteate under nodes or flowers; bracts lanceolate to linear, up to 4 by 0.6 mm. Staminate flowers c. 6 mm diam; pedicel c. 3.5 mm long, c. 0.2 mm thick, pinkish, glabrous; sepals elliptic or obovate, c. 2 by 1 mm, base connate, margin ciliate, apex acute, hirsute outside, glabrous inside; petals obovate, 4–4.5 by 2–2.5 mm, base claw-like, apex rounded, glabrous, dark reddish to maroon-purple; disc glands elliptic or obovate, c. 0.5 by 0.25 mm, narrowed at base and slightly reflected at apex, light orange, glabrous; stamens 3, androphore c. 1 mm long, c. 0.1 mm diam, shortly trifid at top, filaments c. 0.2 mm long; anthers free, divaricate at top, each theca 0.4–0.5 mm long, connective with apically numerous droplets with secretion. Pistillate flowers few, slightly enlarged when fruiting, up to c. 1 cm diam; pedicel (in fruiting flower) c. 7 mm long, thickened towards apex to up to 1 mm diam; sepals long lanceolate to linear, c. 2.5 by 1.2 mm when flowering, accrescent to up to 7.5 by 2 mm in fruit, margin with a few teeth, apex acuminate, outside hirsute, inside glabrous; petals not seen, fallen; disc glands rectangular to semi-orbicular, c. 0.5 by 0.4 mm, rounded or truncate at apex, glabrous; ovary c. 3.5 mm diam, bright dark green, densely hirsute, styles almost indistinct, stigmas 3, completely divided. Fruits c. 1.2 mm diam, green, densely hirsute; wall woody, c. 5 mm thick; columella c. 5 mm long. Seeds c. 6.5 by 5.5 mm, dark brownish when dry, hilum irregularly shaped, more or less triangular, c. 1.5 mm diam.

Distribution — India, China, Laos, Thailand, Malay Peninsula.

Habitat & Ecology — Understorey in evergreen forest to deciduous hardwood or bamboo forest, often near rivers, growing on sandstone to conglomerate bedrock. Altitude: c. 200 m. Flowering: January to March; fruiting: February, July to October.

Note — Trigonostemon flavidus is tentatively treated as a separate species here, but it strongly resembles T. semperflorens from India, of which it might be a synonym. It differs by having more hairs on the upper leaf surfaces.