Trigonostemon victoriae 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 : 215

30. Trigonostemon victoriae R.Y.Yu & Welzen , sp. nov. — Fig. 15 ; Map 10

This species resembles T. capillipes in the pistillate inflorescences and enlarged pistillate sepals, but differs by having racemose staminate inflorescences, staminate flowers with 3 stamens and pistillate flowers with sepals hairy inside and glabrous ovaries. — Type: PNH (Sulit) 12317 (holo L), Philippines, Palawan Province, Victoria Mountains, Panacan, Aborlan .

Small trees, up to 6 m tall, dbh c. 10 cm; flowering branches 2–2.5 mm diam. Outer bark 0.1–0.2 mm thick, pale greyish, somewhat shiny, pubescent near apical buds and glabrescent in mature parts; inner bark 0.1–0.2 mm thick, dark reddish; wood pale yellowish. Stipules subulate, 0.5–1 mm long, often persistent, base pubescent, apex glabrous. Leaves: petiole terete but grooved above, 0.5–3 cm long, pubescent; blade elliptic, 6–11 by 2–4 cm, chartaceous to coriaceous, base acute to rounded, 2 adaxial glands present, often pubescent, margin distantly serrate, teeth glandular, apex acuminate to slightly caudate, upper side glabrous, dark red in dry specimens when young to pale grey and shiny when mature, lower side sparsely pubescent; venation penninerved, often pubescent on the lower side, especially in young leaves, midrib more or less raised above and elevated beneath, nerves 6 – 8 pairs, curved and narrowed along margin, veinlets reticulate. Inflorescences unisexual, racemose, staminate ones c. 5 cm long, c. 0.5 mm diam, appressed pubescent; bracts lanceolate to oblong, 1–3 by 0.3–0.6 mm, appressed pubescent; pistillate inflorescences often with only 1 flower at the top of inflorescences and sometimes a few depauperate buds below; peduncles up to 5 cm long, c. 0.5 mm diam, pubescent; bracts lanceolate to elliptic, 3–4 by 0.3–0.7 mm, pubescent. Staminate flowers (unopened) c. 3 mm diam; pedicel 0.5–1 mm long, c. 0.5 mm diam, pubescent; sepals ovate to elliptic, 1–1.5 by 0.8–1.1 mm, imbricate, margin entire, apex acute to acuminate, pubescent outside; petals orbicular, 0.9–1.1 mm diam, dark purplish, glabrous on both sides; disc lobes semi-orbicular, c. 0.2 by 0.1 mm, fleshy, apex acute; stamens 3, androphore indistinct, anthers ellipsoid, grouped at the top of androphore, c. 0.45 mm long. Pistillate flowers c. 4 mm diam; pedicel c. 3 mm long, c. 0.5 mm diam, sericeous; sepals lanceolate, 2.5–4 by 0.6–1.5 mm when flowering, accrescent to 10–13 by 2.5–4.5 mm when fruiting, margin with a few indistinct teeth, apex acute to acuminate, sericeous on both sides, denser outside; petals elliptic to ovate, 1.1–1.4 by 1–1.2 mm, glabrous except for ciliate margin; disc lobes rectangular, 0.15–0.2 by 0.2–0.25 mm, apex truncate, glabrous; ovary c. 0.65 mm diam, glabrous; styles c. 0.1 mm long, stigmas deeply divided and reniform, arms straight, c. 0.3 mm long. Fruits and seeds not seen.

Distribution — Philippines (Victoria Mountains, endemic).

Habitat & Ecology — Dipterocarp forests, growing on clay, near rivers. Flowering: May.

Note — Only known from the type collection. The mature leaves often turn greyish and are shiny, but this could be a drying artefact. Another useful distinction is that T. victoriae only has a few small bracts along the pistillate inflorescences while its resembling species, T. capillipes , tends to have larger, leaf-like bracts under the pistillate flowers.

Figures

Fig. 15 Trigonostemon victoriae R.Y.Yu & Welzen. a. Two flowering branches; b. pistillate inflorescences; c. pistillate flower (sepals and petals removed); d. staminate inflorescence; e. staminate flower, showing the sepals and petals; f. staminate flower (sepals and petals removed) (all: PNH (Sulit) 12317, L). — Drawing by Esmée Winkel, 2016.