Trigonostemon oblongifolius Merr.

Yu, R. - Y. & Welzen, P. C. van, 2018, A taxonomic revision of Trigonostemon (Euphorbiaceae) in Malesia, Blumea 62 (3), pp. 179-229 : 203-204

20. Trigonostemon oblongifolius Merr. — Map 8

Trigonostemon oblongifolius Merr. (1912) 409; Pax & K.Hoffm. (1914) 407; Merr. (1923) 452; Airy Shaw (1983b) 47. — Type: BS ( Ramos ) 13965 (holo PNH†; iso A, US), Philippines, Luzon, Prov. Cagayan, Abulug River .

Trigonostemon luzoniensis Merr.(1920) 568; (1923) 452; Airy Shaw (1983b) 47. — Type: PNH ( Ramos & Edaño) 33539 (holo PNH†; iso A, K), Philippines, Luzon , Camarines Prov., Paracale.

Small trees, up to 6 m tall; flowering branches terete, 2–4.5 mm diam, whitish and sparsely pubescent when young, buds densely golden pubescent. Bark c. 0.2 mm thick, smooth, pale brownish. Stipules subulate or falcate, 0.5–1 mm long, caducous, pubescent near base. Leaves: petiole terete but often grooved above, 0.5–3.5 cm long, more or less hirsute; blade oblong, 4–23 by 2–6.5 cm, coriaceous, base acute or rounded, margin often slightly recurved, apex acute, upper side paler (when dry), glabrous above and sparsely pubescent beneath; midrib often elevated and hirsute beneath, nerves 6 –12 pairs, curved and often connected along margin, veinlets almost indistinct. Inflorescences: staminate ones (pre-flowered) paniculate thyrses, often axillary, at most few branched and with short glomerate cymes along the main rachis and the lateral branches, main rachis up to 18 cm long, 0.5–1 mm thick, slightly pubescent, bracteate under each branch, bracts lanceolate, c. 2 by 0.6 mm, hirsute outside; secondary branches often short, 0.5–1.5 cm long, cymes scorpioids, clustered, paintbrush- or broom-like, few-flowered, each flower bracteate; the latter lanceolate, up to 0.8 by 0.5 mm, hairy outside; pistillate ones (post-flowered, infructescences) racemose, axillary, c. 5 cm long, glabrescent; bracts lanceolate, c. 1.5 by 0.7 mm, glabrous. Staminate flowers (unopened) c. 1.5 mm diam; pedicel c. 1 mm long, glabrous; sepals orbicular to ovate, c. 1.4 by 1.3 mm, imbricate, slightly hairy outside; petals ovate, c. 0.5 by 0.5 mm, glabrous; disc indistinct; stamens 3, androphore short, hidden, anthers gathered into a head on the top of androphore, c. 0.3 mm long. Pistillate flowers (fruiting): pedicel 2–2.2 cm long, thickened towards apex and scarcely hairy, sepals elliptic, c. 1.2 by 0.8 mm, outside sparsely pubescent near base; ovary villous; stigmas apically cleft, the lobes c. 0.5 mm long. Fruits c. 1 cm diam, appressed-hirsute, warty; wall c. 0.6 mm thick, exocarp partly splitting off; columella c. 5.5 mm long. Seeds c. 6 by 6.5 mm, dark brown; hilum heart-shaped, 2.5–3 by 1.5–1.8 mm.

Distribution — Philippines (Luzon, endemic).

Habitat & Ecology — Flowering: January.

Map 8 Distribution of Trigonostemon oblongifolius Merr. (▼); T. pentandrus Pax & K.Hoffm. (▲); T. polyanthus Merr. (■); T. rufescens Jabl. (●); T. sandakanensis Jabl. (★).

Note — The description of the ovary is based on Merrill (1912). The species has similar-looking inflorescences as T. polyanthus , but the main rachis is more distinct and the secondary rachis is much shorter and condensed than those of the latter species.