Trigonostemon magnificus R.I.Milne

Yu, R. - Y. & Welzen, P. C. van, 2018, A taxonomic revision of Trigonostemon (Euphorbiaceae) in Malesia, Blumea 62 (3), pp. 179-229 : 201

17. Trigonostemon magnificus R.I.Milne — Map 7

Trigonostemon magnificus R.I. Milne (1995b) 51, f. 1 ( ‘ magnificum ’). — Type: W. J. J. O. de Wilde & B. E. E. de Wilde -Duyfjes 19441 (holo K; iso BO, KLU, L, P *), Indonesia, Sumatra, Aceh,c. 75 km WNW of Medan, Gunung Leuser National Park, Sikunder Forest Reserve, Besitang River.

Erect small trees, up to 4.5 m tall; flowering branches 0.8–1 cm diam. Outer bark c. 0.1 mm thick, extremely wrinkled, densely tomentose; inner bark c. 1 mm thick, sap red, sticky; wood yellowish. Stipules subulate, c. 1 mm long, hirsute near base. Leaves: petiole 2.5–9 cm long, 1.7–3 mm diam, tomentellous, wrinkled; blade large, oblong, 18–35 by 7–14 cm, coriaceous, base truncate to acute, often with 2 adaxial subulate glands, margin entire or slightly distantly serrate, apex acuminate, upper side dull green, with a few hairs, lower side very pale, densely tomentose; midrib flat above, elevated and densely tomentose beneath, nerves 14–21 pairs, bow-shaped, veins and veinlets reticulate. Inflorescences bisexual, often axillary, very large panicles, up to 45 cm long, many-flowered, flowers open at same time, pilose; main rachis terete, sometimes angular, 1–2 mm diam, bracteate under each node, bracts linear, up to 8 by 1 mm; secondary and tertiary branches 0.3–0.6 mm thick, often with pistillate flowers above and more staminate flowers below. Staminate flowers small, 3–5 mm diam; pedicel 2.5–3 mm long, c. 0.2 mm diam, pubescent; sepals oblong or lanceolate, 1–2 by 0.5–1 mm, base connate, apex acute to acuminate, often with one globose gland outside, densely sericeous outside and scarcely puberulent inside; petals obovate, c. 3.5 by 1.5 mm, contort, base long cuneate, apex rounded, glabrous outside, rough and slightly papillose inside, dark purplish black; disc glands c. 0.4 by 0.4 mm, somewhat fleshy, apex often recurved; stamens 3, androphore erect, c. 0.8 mm high, anthers ellipsoid, c. 0.5 mm long, free, divaricate at apex. Pistillate flowers larger, c. 6 mm diam, more greenish; pedicel c. 4 mm long, 0.6–0.8 mm diam when flowering, thickened to 1.7 mm and elongated to 4 cm when fruiting, densely hirsutulous; sepals long-triangular or lanceolate, c. 2.5 by 1 mm when flowering, accrescent in fruit to 8.5 by 1.5 mm, with 3 teeth near apex and often with one gland on the tip of each tooth, densely hirsutulous on both sides; petals caducous, as staminate flowers; disc lobes semi-orbicular, c. 0.3 by 0.5 mm, apex rounded, glabrous; ovary c. 2 mm diam, densely hirsute, styles very short, stigmas deeply bifid, arms linear, 1–1.5 mm long, often curved. Fruits c. 1.3 cm diam, densely covered with fine hairs, smooth; wall 0.5–0.8 mm thick, exocarp detaching; columella 6–7 mm long. Seeds c. 6 mm diam; hilum triangular, c. 2.8 by 1.7 mm.

Distribution — Sumatra (endemic).

Habitat & Ecology — Recently logged-over or marshy forests. Flowering and fruiting: August.

Note — A distinct but very rare species, known from two collections, the type and W. J. J. O. de Wilde & B. E. E. de WildeDuyfjes 19280, characterized by the tomentose indumentum, large and spreading inflorescences and sepals hairy on the inside .