Flora of Thailand
Euphorbiaceae
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Baill., Étude Euphorb.: 409. 1858; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.vii: 219. 1914; Airy Shaw, Kew Bull. 26: 350. 197; Whitmore, Tree Fl. Mal. 2: 136. 1973; G.L.Webster, Ann. Missouri Bot. Gard. 81: 86. 1994; Welzen, Blumea 43: 156. 1998; Radcl.-Sm., Gen. Euphorbiacearum: 209. 2001; Welzen in Welzen & Chayam., Fl. Thailand 8, 2: 590. 2007; G.L.Webster in Kubitzki, Fam. Gen. Vasc. Pl. 11: 117, Fig. 26. 2014.— Pseudotrewia Miq., Fl. Ind. Bat. 1, 2: 414. 185, nom. illeg.
Trees, dioecious. Indumentum of simple hairs. Stipules falcately triangular, early caducous. Leaves alternate, simple; blade obovate, papery, symmetric, base cuneate, margin (indistinctly) serrate with a gland in each tooth, upper surface especially basally with glands, lower surface especially subapically with glands, glands few to many, round, black, more or less in line with each other, venation pinnate, nerves looped and joined near margin, veins scalariform, veinlets laxly reticulate. Inflorescences axillary and single (to ramiflorous and in small groups), racemes, pendulous, staminate ones with 2-4 flowers per node, pistillate ones with single flowers per node. Flowers actinomorphic, pedicellate, sepals valvate, reflexed, petals and disc absent. Staminate flowers: sepals (2)3(4), ovate; stamens 16-26, free, anthers 2-locular; pistillode absent. Pistillate flowers: pedicel elongating in fruit; sepals 5, ovate; ovary 3(4)-locular, one ovule per locule. Fruits lobed capsules, smooth, outside tomentose, inside glabrous, woody, thin-walled, septicidal. Seeds without arilloid.
Two species, one ranging from Peninsular S.E. Asia (Myanmar, Thailand) to W. Malesia (up to Philippines, Borneo, Lesser Sunda Islands), the other in Papua New Guinea and N.E. Australia; one species in Thailand. Classification: Subfam.: Acalyphoideae, tribe Acalypheae, subtribe Cleidiinae.
Wetria insignis (Steud.) Airy Shaw, Kew Bull. 26: 350. 1972; Whitmore, Tree Fl. Mal. 2: 136. 1973; Welzen, Blumea 43: 157, fig. 5a-h, map 4. 1998; in Welzen & Chayam., Fl. Thailand 8, 2: 591, Fig. 98, Plate XXXII: 3. 2007.— Trewia macrophylla Blume, Bijdr.: 612. 1825, nom. inval., non Roth, 1821.— Trewia insignis Steud., Nomencl. Bot. ed. 2, 2: 698. 1841, nom. nov.— Wetria trewioides Baill., Étude Euphorb.: 409. 1858, nom. superfl.— Pseudotrewia macrophylla (Blume) Miq., Fl. Ind. Bat. 1, 2: 414. 1859, nom. illeg.— Alchornea blumeana Müll.Arg., Linnaea 34: 167. 1865, nom. superfl.— Agrostistachys pubescens Merr., Philipp. J. Sci. C. Bot. 4: 274. 1909.— Wetria macrophylla (Blume) J.J.Sm., Meded. Dept. Landb. Ned.-Indië 10: 471. 1910, nom. illeg.— Trigonostemon forbesii Pax in Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.iii: 88. 1911.
Trees up to 27 m high. Stipules 6-12 by 2.6-4 mm. Leaves: petiole 0.6-1.5 cm long; blade 9.5-56 by 4-21.5 cm, length/width ratio 2.6-3.2, apex tapering acuminate to cuspidate, tip often mucronulate, glands more or less in line at c. 1/3 from margin, nerves 19-32 pairs. Inflorescences: staminate ones up to 42 cm long, pistillate ones up to 90 cm long. Staminate flowers white or creamy, 5-5.5 mm in diameter; pedicel 2.6-8 mm long, (sub)hirsute; sepals 2.8-3.1 by 1.3-3.2 mm; stamens: filaments 2.8-3 mm long, creamy white, anthers 0.8-1.2 by 0.7-1 mm, connective without or with very short apical appendage less than 0.2 mm long. Pistillate flowers green to green-yellowish, 2.8-4.8 mm in diameter; pedicel up to 10 mm long, hirsute; sepals 1.5-3.2 by 0.3-2 mm; ovary 2.6-4.6 mm in diameter; style 0.2-2 mm long; stigmas 3 (4), 5.8-13 mm long, split after 0.1-3 mm. Fruits 1.3-1.7 by 0.6-1 cm, outside creamy white to grey tomentose, green to yellow-green when immature. Seeds 6-9 mm in diameter; embryo c. 8 by 7 by 6 mm.
T h a i l a n d.— SOUTH-WESTERN: Prachuap Khiri Khan (Huai Yang Waterfall); PENINSULAR: Surat Thani (Khiriratnikhom, Ta Kanawn, Yan Yao), Phuket (Khao Tai).
D i s t r i b u t i o n.— From Myanmar and Thailand to Sumatra, Java (type), Lesser Sunda Islands, Borneo, and the Philippines.
(dots; squares on New Guinea and Australia: Wetria australiensis
P.I.Forst.)
E c o l o g y.— Often common in understorey of primary and secondary mixed Dipterocarp forest, evergreen forest, riverine forest, logged over forest, seldom also in cultivated forest; on ridges, steep slopes, level ground, and along rivers; soil: limestone, sandstone, sandy raised coral, loam, Tertiary granodiorite; usually lime present. Altitude: 5-650(-1830) m.
V e r n a c u l a r.— Tong bai yai (ตองใบใหญ่) (General).