Trigonostemon villosus Hook.f.var. nicobaricus (Chakrab.) N.P.Balakr. & Chakrab.

Yu, R. - Y. & Welzen, P. C. van, 2020, A taxonomic revision of Trigonostemon (Euphorbiaceae) outside Malesia, Blumea 65 (1), pp. 25-52 : 44

29. Trigonostemon villosus Hook.f.var. nicobaricus (Chakrab.) N.P.Balakr. & Chakrab. — sect. Trigonostemon — Map 8

Trigonostemon villosus Hook.f. var. nicobaricus (Chakrab.) N.P.Balakr. & Chakrab. (1991) 629. — Trigonostemon nicobaricus Chakrab. (1984) 203. — Type: Dwivedi 8521 (holo 8521A CAL, barcode CAL0000023667 , iso 8521B, 8521C, 8521D, 8521E, PBL, not seen), India, Great Nicobar Island , 9 km on East-West road.

Small trees, 5–7 m tall; flowering branches 2.8–3.8 mm diam, pubescent when young. Outer bark c. 0.1 mm thick, flaky, pale brownish; inner bark c. 0.1 mm thick, dark reddish; wood pale yellow. Stipules subulate, 0.8–1 mm long, caducous. Leaves: petiole terete but grooved above, 0.3–1 cm long, c. 2.3 mm diam, pubescent; blade oblanceolate, 6.5–23.8 by 2.1–5.6 cm, chartaceous, base abruptly narrowed, rounded to obtuse, 2 adaxial glands present, margin distantly serrate, apex acumi- nate to caudate, upper surface glabrescent, slightly pubescent beneath; venation pinnate; midrib slightly raised above and elevated beneath, secondary veins 13–18 pairs, slightly curved and connected along margin, tertiary veins reticulate. Inflorescences unisexual, terminal or axillary, staminate ones racemose thyrses, pistillate ones racemes; axis up to 4.8–11.7 cm long, 0.4–0.6 mm diam, slightly pubescent; bracts lanceolate to ellip- tic, 1.5–7 by 0.4–0.7 mm, pubescent outside. Staminate flowers (Chakrabarty 1984): pedicel 2–5 mm long, apically 0.4–0.7 mm diam, basally 0.1–0.3 mm diam, puberulous; sepals oblong to triangular, 1–1.5 by 0.7–1.2 mm, margin ciliate, puberulous outside; petals spathulate to obovate, c. 2.5 by 1.2–1.5 mm, blackish crimson, pilose to glabrous; disc glands c. 0.5 mm long; stamens 3, androphore 1–1.3 mm long, anthers ellipsoid to orbicular, 0.6–0.7 mm long. Pistillate flowers (Chakrabarty 1984): pedicel 3.5–4 mm long, apically c. 1 mm diam, basally c. 0.5 mm diam, tomentose; sepals ovate to lanceolate, 4–6 by 1.5–2 mm, margin denticulate to entire, apex acuminate, puberulose outside, without gland or appendage; petals oblong to elliptic, c. 2 by 1–1.2 mm, blackish crimson, sparsely pilose outside; disc glands c. 0.5 mm long; ovary c. 1 mm diam, densely puberulose, stigmas c. 0.8 mm long, erect and apically bifid. Fruits and seeds not seen.

Distribution — India (Great Nicobar Island, endemic).

Habitat & Ecology — Primary hill forests. Flowering: May.

Notes — 1. This variety is only known from the type collec- tion. We have only seen juvenile flowers in the specimen. The description of the staminate and pistillate flowers is based on Chakrabarty (1984).

2. This variety very closely resembles T. villosus Hook.f. var. borneensis (Merr.) Airy Shaw. The geographical distributions of the two varieties are also close (Great Nicobar Island for T. villosus var. nicobaricus and Sumatra as the western limit of T. villosus var. borneensis ). The variety nicobaricus appears different in the somewhat longer leaf blades with an abruptly narrowed base.

Figures

Map 8 Distribution of Trigonostemon fragilis (Gagnep.) Airy Shaw (●), T. lii Y.T.Chang (★), T. murtonii Craib (▲), T. villosus Hook.f. var. nicobaricus (Chakrab.) N.P. Balakr. & Chakrab. (■) and T. xyphophylloides (Croizat) L.K.Dai & T.L.Wu (X).