Trigonostemon longifolius Wall. ex Müll.Arg.

Yu, R. - Y. & Welzen, P. C. van, 2018, A taxonomic revision of Trigonostemon (Euphorbiaceae) in Malesia, Blumea 62 (3), pp. 179-229 : 197-199

14. Trigonostemon longifolius Wall. ex Müll.Arg. — Fig. 6 ; Map 6

Trigonostemon longifolius Wall. (ex Baill. (1858) 341, nom. inval., still nom. nud.) ex Müll.Arg. (1866) 1108; Kurz (1877b) 406 (‘longifolium ’); Hook.f. (1887) 396; Pax & K.Hoffm. (1911) 88, f. 28; Ridl. (1924) 264; Jabl. (1963) 162; Airy Shaw (1972a) 347; Whitmore (1973) 136; Airy Shaw (1981) 355; Chantar. (2005) 26; (2007) 579, f. 94. — [ Croton longifolius Wall., Numer. List (1847) 7717, nom. nud., non Müll.Arg. (1873) 170.] — Lectotype (designated here): Wallich 7717 (K, barcode K000959328; iso BR, G, GH, K, barcode K000959327), Malaya, Penang Island. Syntypes: Griffith KD 4797 (K), Malaya, Malacca; Griffith KD 4798 (K), India, Tenasserim and Andamans.

? Athroisma dentatum Griff. (1854a) 478 (‘ dentatis ’); (1854b) pl. 585, f. 4. — Type: Griffith s. n.?, Nov. 1834 (K?), Mergue,Madamaca (see Hooker 1887: 396, Pax & Hoffmann 1911: 88).

? Athroisma serratum Griff. (1854a) 477 (‘ serratis ’); (1854b) pl. 585, f. 9. — Type: Griffith s. n.? (K?), Mergue,Tenasserim (see Airy Shaw 1972a:347).

Croton longipedunculatus Elmer (1908) 311. — Trigonostemon longipedunculatus (Elmer) Elmer (1911) 1306;Pax & K.Hoffm.(1914) 408;Merr.(1923) 452; Airy Shaw (1983b) 47; R.I. Milne (1995a) 38. — Type: Elmer 7264 (holo PNH†; iso A, BO, E, G, K), Philippines, Leyte, Prov. of Leyte, Palo.

Trigonostemon oblanceolatus C.B.Rob. (1911) 337; Pax & K.Hoffm. (1914) 407; Merr. (1923) 452; Airy Shaw (1983b) 47. — Type: Williams 2185 (holo PNH†; iso K, NY, US), Philippines, Mindanao, Zamboanga District, Sax River .

Prosartema gaudichaudii Gagnep. (1925a) 468, non Trigonostemon gaudichaudii (Baill.) Müll.Arg.(1865) 213. — Trigonostemon gagnepainianus Airy Shaw (1978) 415. — Syntypes: Gaudichaud 167 (P*), Vietnam, Tourane; Poilane 8306 (P*), Vietnam, from Nhatrang to Ninh Hoa; 10220 (P*), Vietnam, prov. de Quang Tri, Mai-lanh; Poilane 10446 (P*, K), Vietnam, Prov. de Quang Tri, Dent du Tigre.

Trigonostemon elmeri Merr. (1929) 162; Jabl. (1963) 162; Airy Shaw (1975) 202;R.I. Milne (1995a) 27,in key,29,in key,41. — Type: Elmer 20936 (holo PNH†; iso A, BISH*, BM, BO, BR*, CAS*, CM*, G*, HBG*, K, L 2 sheets, M*, MICH*, NY*, P*, PH *, S*, SING, U), Sabah, near Tawao.

Trigonostemon howii Merr. & Chun (1935) 262; H. S. Kiu (1996) 163. — Type : F. C. How 70940 ( A *, IBSC *, K, NY *, US*), China, Hainan .

Trigonostemon ionthocarpus Airy Shaw (1968) 407; (1975) 203; R.I. Milne (1995a) 27, in key, 29, in key. — Type: SAN (Meijer) 19672 (holo K; iso BRI *, SING), Sabah, Sandakan Dist., Mile 17, Gum-Gum .

Trigonostemon matangensis R.I. Milne (1994) 445,f. 1; (1995a) 27,in key,29, in key. — Type: Ridley s. n. (holo K), Sarawak (SW), 1st Division, Matang.

Trigonostemon longipedunculatus (Elmer) Elmer var. mollis R.I. Milne (1995a) 27, in key, 29, in key, 40. — Type: SAN (James Ah Wing) 38218 (holo K; iso L, SAN ), Sabah, Sandakan District, Sekong Kechil, Sepagaya, Sandakan Bay.

Trigonostemon sanguineus auct. non Gagnep.: Ridl. (1926) 80. — Trigonostemon ridleyi Jabl. (1963) 165, f. 8. — Type: Boden-Kloss 14697 (holo SING; iso K), Sumatra, Sipora Island of Mentawi Group .

Small trees, 1–5 m tall, stem up to 7 cm diam; flowering branches 2–5(–7) cm diam. Outer bark 0.1–0.25 mm thick, smooth, pubescent to hispid when young, whitish to brownish; inner bark 0.2–0.4 mm thick, yellowish to reddish brown, soft; sapwood 0.8–1.5 mm thick, white to dark brownish; heartwood 2–3 mm diam. Stipules linear to hook-like, 2–8.5 by 0.3–1 mm, often pubescent. Leaves: petiole terete, 0.4–3.5 cm long, often wrinkled, hispid; blade oblanceolate, (10–)12–28(–46) by (2.8–)4–10(–15) cm, membranous to chartaceous to coriaceous, base cuneate to round, margin distantly serrate, apex acuminate to slightly caudate, upper side glabrous to slightly pubescent, lower side often pubescent to hispid; midrib robust, elevated on both sides, nerves (9–)11–16(–33) pairs, often slightly curved and connected along margin, veins scalariform, veinlets reticulate. Inflorescences uni- or bisexual, axillary or terminal, loose or condensed, per node a single flower or short cymes, rachis (7–)15–30(–55) cm long, 0.5–4 mm diam, pubescent; bracts lanceolate to linear, 3–8 by 0.3–1 mm, pubescent. Staminate flowers 4–5 mm diam; pedicel 1.5 ( Thailand, Malay Peninsula, Sumatra)–5 (Borneo) mm long, 0.1–0.2 mm diam, pubescent, base articulate; sepals elliptic, 1.2–2 by 0.7–1 mm, green, margin entire, apex rounded, pubescent outside, glabrous inside; petals spathulate to obovate, 2–2.5 by 1.2–1.7 mm, pinkish to bluish black, base slightly claw-like, sometimes with 2 gland lobes ( Thailand, Malay Peninsula, Sumatra), margin entire, apex rounded, smooth outside, often rough and papillose inside; disc annular, 0.2–0.4 mm wide, margin often 5-notched; stamens 3, androphore c. 0.4 mm long, trifid at top, anthers free, divaricate, connective sometimes protruding at top ( Thailand, Malay Peninsula, Sumatra). Pistillate flowers 4–5 mm diam; pedicel slightly thickened towards apex, 1.7–3 ( Thailand, Malay Peninsula, Sumatra)–9 (Borneo) mm long, apically 0.5–1 mm diam; sepals elliptic to lanceolate, 1.2–1.8 by 0.8–1.5 mm, margin entire, apex rounded to acute, pubescent outside, glabrous inside; petals and disc as staminate flowers; ovary c. 0.7 mm diam, densely pubescent, glabrescent, slightly ( Thailand, Malay Peninsula, Sumatra, Borneo, Philippines) to extremely (Borneo) warty; styles short, often indistinct, trifid; stigmas bifid into 2 flattened lobes. Fruits 1.2–1.4 cm diam, green, pubescent, glabrescent, slightly to extremely warty; sepals persistent, not accrescent; wall 0.4–0.6 mm thick, exocarp partly splitting off; columella 5.5–6 mm long. Seeds 6.5–7 by 6–6.5 mm; hilum elliptic to rhombic to heart-shaped, 2–4.5 by 2.5–4 mm.

Distribution — China, India, Thailand, Vietnam, Malay Peninsula, Sumatra, Borneo, Philippines.

Habitat & Ecology — Primary to logged forests, flat land to hill sides, sometimes near rivers, growing on black soil or sandy or stoney clay. Altitude: 15–1000 m. Flowering and fruiting: all year round.

Notes — 1. The staminate flowers are cauliflorous on one specimen (Wenzel 1513, BM) .

2. Most of the species in this complex, now synonymised, were based on slight differences, but all show the same essential similarities including the short petiole, spike-like inflorescences and the more or less warty fruits. All of these indicate that they are conspecific. Two kinds of forms can be distinguished, though there is overlap via intermediates that cannot be placed: a form, often identified as T. elmeri , mostly distributed in Thailand, Malay Peninsula, Sumatra and parts of Borneo with short pedicel (1.5–3 mm long), petals with 2 glands at base and densely hairy but slightly warty fruits; another form, often identified as T. ionthocarpus , mainly in parts of Borneo and the Philippines with longer but thinner pedicel (3–9 mm long), petals with papillate hairs inside but without a basal gland and sometime extremely warty fruits.A molecular phylogeny of this species complex may enlighten an infraspecific distinction between the forms.

Figures

Map 6 Distribution of Trigonostemon longifolius Wall. ex Müll.Arg.

Fig. 6 Trigonostemon longifolius Wall. ex Müll.Arg., from Kabili-Sepilok Forest Reserve, Sandakan, Sabah, Malaysia (a), and Kuala Belalong, Temburong, Brunei (b–e). a, b. Growing habit; c. staminate flowers; d. pistillate flower; e. fruits. — Photos by Ren-Yong Yu.