Trigonostemon wetriifolius Airy Shaw & Ng

Yu, R. - Y. & Welzen, P. C. van, 2018, A taxonomic revision of Trigonostemon (Euphorbiaceae) in Malesia, Blumea 62 (3), pp. 179-229 : 222

33. Trigonostemon wetriifolius Airy Shaw & Ng — Fig. 19 ; Map 10

Trigonostemon wetriifolius Airy Shaw & Ng (1978) 237. — Type: KEP FRI (F. S. P. Ng) 27157 (holo K; iso KEP ), Malaysia, S Pahang, Lesong Forest Reserve in proposed Endau-Rompin National Park.

Small trees, 3 m tall, stem single, erect, 10–12 mm thick; flowering branches up to 1.2 cm diam, adventitious roots present, 0.5–1 mm thick, puberulent. Bark c. 0.6 mm thick, brownish to greyish, smooth to fissured; sapwood c. 2 mm thick, yellowish; heartwood 3–4 mm diam, whitish. Stipules subulate, 3–4 by c. 1 mm, apex acute, puberulent, caducous. Leaves clustered on the top of the stem; petiole c. 1.8 cm long, c. 5 mm diam, slightly pubescent; blade spathulate to oblanceolate, 35–62 by 9–19 cm, chartaceous, base rounded, adaxial glands not seen, margin distantly serrate, apex acuminate, both sides glabrous; venation penninerved, slightly pubescent on lower side, midrib robust, slightly raised on both sides, nerves 27–30 pairs, curved, veins scalariform, veinlets reticulate. Inflorescences axillary, 1–3 cm long, few-flowered, 1 pistillate flower at top and a few staminate flowers below, rachis appressed puberulent; bracts subulate, 1–5 mm long, puberulent. Staminate flowers c. 4 mm diam; pedicel 1–2 mm long, glabrous; sepals rounded to ovate, 2–3 by 1–2 mm, apex obtuse, pubescent outside, inside glabrous; petals ovate, 1–1.5 by 1–1.5 mm, fleshy, glabrous, yellowish except reddish at base, apex obtuse; disc lobes more or less square, fleshy, c. 0.3 by 0.5 mm; stamens 5, androphore short, hidden, anthers ellipsoid, c. 0.5 mm long, divaricate at apex. Pistillate flowers (unopened): pedicel, sepals, petals and disc as staminate flowers; ovary glabrous; styles short, stigmas slightly bifid. Fruits and seeds unknown.

Distribution — Malay Peninsula (Lesong Forest Reserve, endemic).

Habitat & Ecology — Primary lowland forest under logging. Flowering: September.

Note — Only known from the type specimen. Two slides of the plant (see Fig. 19 , taken by Francis Ng) are attached with the type specimen. Descriptions of staminate flowers are mainly based on the slides, thus the measurements might not be exactly accurate, since a scale was unavailable; other parts of descriptions are based on Airy Shaw & Ng (1978). The species resembles T. detritiferus in morphology and living strategy, for more details, see notes under T. detritiferus .

Figures

Fig. 19 Trigonostemon wetriifolius Airy Shaw & Ng, Lesong Forest Reserve, Malay Peninsula. a. Growing habit, leaves arranged in whorls at top of main stem and trap fallen leaves; b. cauliflorous staminate flower. — Used with permission from Francis Ng.