Trigonostemon diffusus Merr.

Yu, R. - Y. & Welzen, P. C. van, 2018, A taxonomic revision of Trigonostemon (Euphorbiaceae) in Malesia, Blumea 62 (3), pp. 179-229 : 194

8. Trigonostemon diffusus Merr. — Map 3

Trigonostemon diffusus Merr.(1928) 525;Jabl.(1963) 164; R.I. Milne (1995a) 27, in key, 29, in key, 46. — Type: MjÖberg 145 (BM, K, UC*), Sarawak, Mount Poi.

Shrubs or small trees, at least up to 6 m tall; flowering branches terete, 2–2.5 mm diam. Outer bark c. 0.1 mm thick, pale, slightly hirsute in young parts, glabrous and wrinkled in older parts; inner bark c. 0.2 mm thick, reddish brown; wood pale yellowish. Stipules falcate, 0.6–1 mm long, pubescent. Leaves: petiole 1–9 cm long, slightly pubescent, grooved above, thickened at base and top; blade oblong, 12–19 by 3.5–5.5 cm, membranous, sometimes slightly asymmetric, base acute and often with 2 adaxial glands, margin distantly crenate-dentate, teeth somewhat nipple-like, apex acuminate to caudate, surfaces olive-green, glabrous above and slightly hirsute beneath; midrib raised on both sides, slightly hirsute beneath, nerves 10–12 pairs, veins reticulate. Inflorescences paniculate, large and diffuse, much developed and branched but few flowers present, up to 35 cm long, slightly hirsute; bracts triangular, up to 0.6 by 0.3 mm, abaxial surface slightly pubescent. Staminate flowers (unopened) caducous, c. 1.7 mm diam; pedicel 2–3 mm long, 0.1–0.2 mm diam, glabrescent; sepals elliptic to ovate, 0.9–1.2 by 0.8–1 mm, slightly pubescent outside; petals elliptic, c. 1.5 by 1 mm, dark red or purple, margin slightly ciliate, apex rounded, both sides glabrous; disc lobes almost trapezoid, c. 0.2 by 0.3 mm; stamens 3, androphore c. 0.5 mm long, anthers ellipsoid, c. 0.6 mm long, connectives apically with numerous droplets with secretion. Pistillate flowers and fruits unknown.

Distribution — Borneo ( Sarawak, endemic).

Habitat & Ecology — Forests near the foot of mountains. Altitude: 760 m. Flowering: September.

Notes — 1. The species is only known from two collections (the type and J. W. Purseglove P. 4702). It is mainly distinguished by its large, diffuse, few-flowered inflorescences .

2. Trigonostemon diffusus subsp. condensus , should be synonymised under T. polyanthus , see note 3 under T. polyanthus .