Trigonostemon merrillii Elmer

Yu, R. - Y. & Welzen, P. C. van, 2018, A taxonomic revision of Trigonostemon (Euphorbiaceae) in Malesia, Blumea 62 (3), pp. 179-229 : 203

19. Trigonostemon merrillii Elmer — Map 7

Trigonostemon merrillii Elmer (1911) 1304;Pax & K.Hoffm.(1914) 407;Merr. (1923) 452; Airy Shaw (1983b) 47; R.I. Milne (1995a) 27, in key, 29, in key, 44. — Type: Elmer 12819 (holo PNH†; iso BISH*, BM, BO, F*, G*, HBG*, L, MO*, NY*, US *), Philippines, Palawan, Puerto Princesa (Mt Pulgar).

Shrubs, 2–3 m tall, stem up to 2.5 cm diam; flowering branches terete, up to 5 mm diam. Indumentum densely sericeous, especially on young parts. Outer bark 0.1–0.2 mm thick, pale brownish, hairy; inner bark 0.2–0.3 mm thick, reddish black, with sap; sapwood c. 0.4 mm thick, reddish brown; heartwood c. 2 mm diam, pale yellowish or brownish; pith empty. Stipules lanceolate to linear, 1–3 mm long, sericeous, caducous. Leaves: petioles terete or often angled, 1–2.5 cm long, densely sericeous; blade elliptic, 10–24 by 5–9.5 cm, chartaceous, base rounded or cordate, 2 adaxial glands present but often covered by silky hairs, margin distantly serrate, teeth often apiculate, falcate when young, apex acute to acuminate to caudate, upper surface greenish, paler beneath, both sides covered by long silky hairs; midrib slightly raised above and much elevated beneath, more densely sericeous, nerves 10–13 pairs, curved and connected near margin, veins and veinlets reticulate, sometimes obscure. Inflorescences: staminate ones thyrsoid with glomerulus along the main rachis, peduncle slender, 8–9 cm long and 0.4–0.7 mm diam, sericeous, with a few depauperate glomerulus below; involucral bracts subulate, at the base of inflorescences, c. 1.2 mm long, base hairy, bracts lanceolate, under each node, 1.1–3 mm long, sericeous; pistillate inflorescences racemose, main rachis slender, up to 12 cm long, c. 0.6 mm diam, sericeous; bracts as in staminate inflorescences. Staminate flowers 2.8–3.5 mm diam; pedicels c. 1 mm long, 0.15 mm diam, glabrescent; sepals unequal, elliptic to spathulate, 0.9–1.3 by 0.7–0.8 mm, narrowed near base, margin entire or slightly undulate, acute to rounded at apex, more or less pubescent outside; petals spathulate, 1.3–2.2 by 1.2–1.6 mm, dark purple, base cuneate, apex rounded, glabrous on both sides; disc cupular, slightly wrinkled, 5-toothed, each tooth rectangular, c. 0.2 by 0.2 mm, apex truncate, glabrous; stamens 3, androphore erect, 0.4–0.5 mm high, anthers ellipsoid, 0.25–0.35 mm long, gathered on the top of androphore, slightly divaricate at apex, connectives apically with some droplets (expanded cells) with secretion. Pistillate flowers unseen. Fruits c. 1.25 cm diam, glabrous; sepals not much accrescent. Seeds streaked or conspicuously mottled.

Distribution — Philippines (endemic).

Habitat & Ecology — Lowland dipterocarp forest. Altitude: 15 m. Flowering: March.

Note — The species resembles T. oblongifolius in the male inflorescences but differs from the latter by the blade being hairy on both sides. The description of fruits is based on Elmer (1911).