Trigonostemon capillipes (Hook.f.) Airy Shaw

Yu, R. - Y. & Welzen, P. C. van, 2018, A taxonomic revision of Trigonostemon (Euphorbiaceae) in Malesia, Blumea 62 (3), pp. 179-229 : 191

6. Trigonostemon capillipes (Hook.f.) Airy Shaw — Map 4

Trigonostemon capillipes (Hook.f.) Airy Shaw (1967) 413; (1972a) 345; Whitmore (1973) 135; Airy Shaw (1975) 202; R.I. Milne (1995a) 28, in key, 29,in key,45;Chantar. (2005) 24; (2007) 576. — Dimorphocalyx capillipes Hook.f. (1887) 404; Pax & K.Hoffm. (1911) 33; Ridl. (1924) 266. — Type: Lobb s. n. (holo K, barcode K000894763), Singapore.

Trigonostemon pachyphyllus Airy Shaw (1971) 546; Chantar. (2005) 27; (2007) 581. — Type: Kerr 19429 (holo K), Thailand, Chanthaburi, Khao Soi Dao .

Trigonostemon sp. nov., aff. indicus (Baill.) Müll.Arg. : Jabl. (1963) 168. — Voucher: Kiah 35303 (BO, K, L, SING), Malaysia, Perlis, Bukit Kaki.

Shrubs or small trees, 1–8 m tall; flowering branches 1.7–3.2 mm diam. Bark 0.1–0.2 mm thick, brownish to greyish, slightly pubescent near young parts, smooth; wood pale yellowish. Stipules subulate, 0.5–1 mm long, caducous, pubescent at base. Leaves: petiole 0.3–1(–2.5) cm long, grooved above, pubescent; blade oblanceolate, oblong or obovate, 9–20 by 3–7 cm, chartaceous, base acute to obtuse, with 2 adaxial glands, margin distantly serrate, teeth small, falcate, apex acuminate, upper side glabrous, lower side paler, slightly pubescent and more or less ciliate along margin; midrib slightly raised on both sides, nerves 9 –12 pairs, connected along margin, small veins reticulate. Inflorescences: staminate ones thyrsoid, branched (paniculate), 4–8 cm long, glabrescent, axillary or cauliflorous; bracts leaf-like, elliptic to oblong, up to 10 by 4 mm, slightly pubescent abaxially; pistillate inflorescences cymose, peduncles slender, 1–15 cm long, 0.2–0.5 mm diam, often only one flower at top (sometimes with few depauperate flowers below); bracts as in staminate inflorescences, 4–20 by 1–5 mm. Staminate flowers c. 6 mm diam; pedicel 0.2–0.4 cm long, 0.1 (middle part)–0.2 (top) mm thick, glabrescent or

Map 4 Distribution of Trigonostemon capillipes (Hook.f.) Airy Shaw (●); T. detritiferus R.I.Milne (★); T. flavidus Gagnep. (■).

slightly pubescent; sepals elliptic, c. 1.6 by 1.2 mm, pale green, apex rounded or slightly notched, under the notch often with a gland on outside surface, but sometimes faint or only a few expanded cells; petals elliptic or spathulate, 3–3.5 by 1.5–1.8 mm, base narrowed, acute to cuneate, sometimes claw-like, entire, apex rounded, dark purple, in mature flowers with an orange flame-like honey mark in the middle of the lower part, smooth and glabrous outside, rough and papillose inside; disc lobes almost obtrapezoid, c. 0.35 by 0.3 mm, c. 0.1 mm thick, apex thickened and slightly reflexed, glabrous; stamens 5, androphore c. 0.6 mm long, c. 0.2 mm diam, 5-branched at c. 0.1 mm below apex, filaments c. 0.1 mm long, anthers c. 0.7 mm long, pinkish, divaricate, connectives apically with numerous dark reddish droplets (or expanded cells) with secretion. Pistillate flowers c. 1 cm diam, pedicel slightly thickening towards apex, 6–9 mm long, apically c. 0.7 mm diam when flowering, in fruit accrescent to 1.5 cm long and apically c. 2 mm diam, slightly pubescent; sepals oblong to lanceolate, c. 4 by 2 mm when flowering, accrescent to 5–15 by 2–6 mm in fruit, pale green, margin slightly serrate, teeth glandular, apex acute to acuminate; petals as staminate flowers but larger, c. 5 by 2 mm; disc lobes rectangular, c. 0.4 by 0.6, apex truncate, corners rounded; ovary c. 1 mm diam, densely hairy, style c. 0.1 mm long, often indistinct, stigmas nearly completely divided, c. 0.9–1 mm long, free arms c. 0.8 mm long, slightly thickened abaxially. Fruits c. 1.2 cm diam, finely hairy; sepals and stigmas persistent, stigmas flattened at base, abaxially hairy; wall c. 0.4 mm thick, exocarp not detaching; columella c. 5 mm. Seeds c. 6 mm diam; hilum heart-shaped, 1–1.6 by 1.4–1.5 mm.

Distribution — Thailand, Malay Peninsula.

Habitat & Ecology — Lowland rainforest to mangrove forest. Altitude: 0– 300 m. Flowering: December to April; fruiting: December to February.

Note — Airy Shaw (1967) transferred this species from Dimorphocalyx to Trigonostemon without any information on staminate flowers in the type collection. Nevertheless, it can be recognized by the often single-flowered pistillate inflorescences and much enlarged sepals in pistillate flowers, and it differs from the newly proposed Philippine species T. victoriae by having thyrsoid staminate inflorescences and 5 instead of 3 stamens.