Trigonostemon scopulatus R.Y.Yu & Welzen, 2018

Yu, R. - Y. & Welzen, P. C. van, 2018, A taxonomic revision of Trigonostemon (Euphorbiaceae) in Malesia, Blumea 62 (3), pp. 179-229 : 210-211

26. Trigonostemon scopulatus R.Y.Yu & Welzen , sp. nov. — Fig. 14 ; Map 10

This species resembles T. villosus , but there are two kinds of inflorescences, those on the leafless parts are contracted and those in the axils of still present leaves are elongated and have the flowers especially in the upper part and may resemble brooms, the ovary is glabrous. — Type: KEP FRI (P. F. Cockburn) 7859 (holo L; iso K, KEP, SING ), Malaysia, Johore, Ulu Endau, Labis FR, Compt. 277. Paratypes: KEP FRI (F. S. P. Ng) 5207 ( KEP , L), Malaysia, Johore, Mersing, Arong FR, Compt. 90; Joseph Lai & Ali Ibrahim LJ 22 (SING), Singapore, Mandai Forest, next to Mandai Columbarium; Joseph Lai & Ali Ibrahim LJ 80 (SING), Singapore, Mandai, Central Catch- ment Nature Reserve.

Small trees, up to 3 m tall; flowering branches c. 3.5 mm diam, sometimes hollow. Outer bark 0.1–0.2 mm thick, dark brownish, tomentellous; inner bark 0.1–0.3 mm thick, dark reddish to blackish; sapwood 1.5–2 mm thick, brown; heartwood c. 1.5 mm diam, brown. Stipules subulate, c. 0.5 mm long, often covered with hairs. Leaves: petiole terete, 2.5–12 cm long, hispidulous; blade oblong, 12–26 by 4–7.5 cm, chartaceous, base narrowly cordate, glands not seen, margin entire or slightly, distantly serrate, apex acuminate, upper side dark brownish to black (when dry), glabrous, lower side brown (when dry), papillate-hispid; venation penninerved, papillose hispid on lower side, midrib flat above and elevated beneath, nerves 10–13 pairs, straight or slightly curved, branched and connected along margin, veins scalariform, veinlets reticulate. Inflorescences bisexual, in the leafless parts fascicled, in the axils of still present leaves elongated and racemose or thyrsoid, with the flowers concentrated at the upper part of the rachis and broom-like, rachis up to 10 cm long, 0.8–1 mm diam, densely hispid; bracts lanceolate, 4–5 by 0.6–1.2 mm, apex acuminate, densely hispid outside, glabrous inside. Staminate flowers 2.5–3.5 mm diam; pedicel 4.5–5.5 mm long, 0.2–0.3 mm diam, hispidulous; sepals lanceolate to linear, 1–1.5 by 0.2–0.3 mm, margin entire or slightly serrate, apex acuminate, outer surface hispid and with few whitish oil-like spots; petals elliptic, 1.2–1.5 by 0.7–0.8 mm, dark red to purple, glabrous on both sides; disc lobes rectangular to obtrapezoid, c. 0.2 by 0.2 mm, apex truncate, often slightly revolute; stamens 3, androphore c. 0.4 mm long; anthers gathered on the top of androphore, ellipsoid, c. 0.5 mm long. Pistillate flowers 0.45–0.5 mm diam; pedicel 6–8 mm long, 0.4–0.5 mm diam, densely hispid; sepals lanceolate, 2.5–3 by c. 0.5 mm, margin entire, apex acuminate, hispid outside, glabrous inside; petals elliptic, 2.4–3 by 1–1.5 mm, dark red, margin entire, base and apex acute, glabrous outside, rough and slightly papillate inside; disc obtrapezoid, c. 0.45 by 0.45 mm, apex truncate; ovary c. 0.8 mm diam, glabrous; styles short, sometimes indistinct, c. 0.1 mm long; stigmas deeply bifid, arms 0.6–0.7 mm long, bent, thickened abaxially and sagittate near base. Fruits and seeds unknown.

Distribution — Malay Peninsula (endemic, only found in Johor, Malaysia and Singapore).

Habitat & Ecology — Disturbed forest near logging road; moist gully. Altitude: low. Flowering: March.

Figures

Fig. 14 Trigonostemon scopulatus R.Y.Yu & Welzen. a. Flowering branch; b. bark; c. cauliflorous inflorescence; d. apex of inflorescence; e. pistillate flower (3 sepals and 3 petals removed);f. staminate flower (2 sepals and 3 petals removed) (all: KEP FRI (P.F. Cockburn) 7859, L). — Drawing by Esmée Winkel,2016.