Flora of Thailand Euphorbiaceae

 

85. Trigonostemon

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Genus description

Identification key

Species descriptions

Trigonostemon

Blume, Bijdr.: 600. 1826; Fl. Javae: viii. 1828, nom. cons.; Baill., Étude Gén. Euphorb.: 340. 1858; Müll.Arg. in DC., Prodr. 15, 2: 1105. 1866; Benth. in Benth. & Hook., Gen. Pl. 3: 298. 1880; Hook.f., Fl. Brit. Ind. 5: 395. 1887; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.iii: 85. 1911; Gagnep. in Lecomte, Fl. Indo-Chine 5: 309. 1925; Pax & K.Hoffm. in Engl. & Harms, Nat. Pflanzenfam. ed. 2, 19C: 169. 1931; Backer & Bakh.f., Fl. Java 1: 495. 1963; Airy Shaw, Kew Bull. 20: 47. 1966; Kew Bull. 21: 407. 1968; Kew Bull. 23: 126. 1969; Kew Bull. 25: 545. 1971; Kew Bull. 26: 344. 1972; Whitmore, Tree Fl. Malaya 2: 134. 1973; Airy Shaw, Hooker’s Icon. Pl. 38: t. 3721. 1974; G.L.Webster, Ann. Missouri Bot. Gard. 81: 108. 1994; Philcox in Dassan., Rev. Handb. Fl. Ceylon 11: 110. 1997; Radcl.-Sm., Gen. Euphorb.: 307. 2001; Chantar. in Welzen & Chayamarit, Fl. Thailand 8, 2: 573. 2007. — Enchidium Jack, Malayan Misc. 2(7): 89. 1822, nom. rej.; Baill., Étude Gén. Euphorb.: 652: 1858. — Telogyne Baill., Étude Gén. Euphorb.: 652: 1858. — Tylosepalum Kurz ex Teijsm. & Binn., Natuurk. Tijdschr. Ned.-Indië 27: 50. 1864. — Actephilopsis Ridl., Bull. Misc. Inform., Kew 1923: 360. 1923.

Shrubs or small trees, monoecious. Stipules minute, triangular or subulate, caducous. Leaves spiral at the end of the branches, rarely subopposite; usually triplinerved. Inflorescences raceme-like, spikes or panicles, rarely cymes, axillary or terminal, often apparently unisexual. Flowers pedicelled; sepals 5; petals 5, dark purplish red, red, orange-yellow or white, usually drying blackish; disc usually entire and annular or cupular, or consisting of 5 free glands. Staminate flowers with 3 or 5 stamens, filaments united in to a column, but apically free and spreading; pistillode absent. Pistillate flowers with 3-locular ovary; one ovule per locule; style bifid or twice bifid. Fruit a capsule, 3-lobed, smooth, glabrous or pubescent, splitting into 3 bivalved parts, calyx persistent, sometimes enlarged. Seeds globose to 3-gonous-ovoid.

    A genus of 50-60 species, distributed from India and Sri Lanka to China, SE Asia, New Guinea and Queensland. Fourteen species in Thailand.

Key to the species

1. Trigonostemon albiflorus Airy Shaw, Kew Bull. 25: 547. 1971; Chantar., Thai Forest Bull. (Bot.) 33: 23. 2005; in Welzen & Chayamarit, Fl. Thailand 8, 2: 574, Fig. 92. 2007. — Trigonostemon leucanthus Airy Shaw, Kew. Bull. 25: 548. 1971.

Shrubs up to 3 m high; branchlets terete, sparsely pubescent, glabrescent. Stipules subulate, c. 1 mm long. Leaves: petiole 2-6 cm long, pilose; blade elliptic or oblong elliptic, 13-30 by 3.5-9 cm, membranous to thinly chartaceous, base broadly cuneate, margin entire and minutely sinuate, apex acuminate or acuminate caudate, sparsely hairy on both sides; venation triplinerved, nerves in 6-9 pairs. Inflorescences paniculate, lax, bisexual, terminal and axillary, up to 22 cm long, pilose, glabrescent; bracteoles subulate, 2.3-5 by c. 0.5 mm, adpressed hairy outside, glabrous inside. Staminate flowers: pedicel 1-7 mm long, glabrous; sepals obovate or oblong, 2-3 by 1-2 mm, membranous, pilose outside, glabrous inside; petals spathulate to obovate, 3-3.5 by 1-2 mm, membranous, white; disc annular; stamens 3, staminal column 0.6-2 mm long, anthers 0.3-0.5 mm long. Pistillate flowers: pedicel 1-2 cm long, glabrous or sparsely pubescent near the top; sepals ovate 1.5-2.5 by 1.2-1.5 mm, margin hyaline, sparsely pilose along mid-line and apex outside, glabrous inside; petals ovate, 1.5-2 by 1-1.5 mm; disc annular; ovary glabrous; style 0.5-1 mm long. Fruits: pedicel 1.3-2 cm long; immature capsule depressed globose, glabrous, 5-6 mm in diameter. Seeds flattened and trigonous, c. 8 by 9 mm.

    Thailand.— NORTHERN: Chiang Mai (Doi Chiangdao), Nan, Lampang (Wang Nua, WINIT 1704-holotype K, isotypes BKF, BM); SOUTH-EASTERN: Chanthaburi (Soi Dao).

    Distribution.— China (Kwangsi).

    Ecology.— In evergreen forest. Altitude: 110-1,800 m.

2. Trigonostemon aurantiacus (Kurz ex Teijsm. & Binn.) Boerl., Handl. Fl. Ned. Ind. 3 (1): 284. 1900; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.iii: 93. 1911; Airy Shaw, Kew Bull. 28: 126. 1969; Chantar., Thai Forest Bull. (Bot.) 33: 23. 2005; in Welzen & Chayamarit, Fl. Thailand 8, 2: 576. 2007. — Tylosepalum aurantiacum Kurz ex Teijsm. & Binn., Natuurk. Tijdschr. Ned.-Indië 27: 50. 1864. — Codiaeum aurantiacum (Kurz ex Teijsm. & Binn.) Müll.Arg. in DC., Prodr. 15, 2: 1118. 1866. — Actephila aurantiaca (Kurz ex Teijsm. & Binn.) Ridl., Bull. Misc. Inform., Kew 1923: 360. 1923; Fl. Malay Penins. 3: 197. 1924. — Actephilopsis malayana Ridl., Bull. Misc. Inform., Kew 1923: 361. 1923; Fl. Malay Penins. 3: 252. 1924; M.R.Hend., J. Malay Br. Roy. As. Soc. 17: 68. 1939. — Trigonostemon malayanus (Ridl.) Airy Shaw, Kew Bull. 20: 413. 1966.

Shrubs or small trees up to 3 m high; branchlets sparsely hairy, glabrescent. Stipules triangular, 0.8-1 mm long. Leaves: petiole 5-15 mm long, sparsely hairy, glabrescent; blade ovate, obovate or elliptic, 19-27.5 by 5.5-10.5 cm, chartaceous or coriaceous, base cuneate, margin shallowly denticulate or distantly crenate-serrate, apex shortly blunt acuminate, both surfaces glabrous, sparsely hairy when young; venation penninerved, rarely triplinerved, nerves in (10-)13-15 pairs. Staminate inflorescences in groups, axillary, 6-15 cm long. Staminate flowers: pedicel c. 0.5 mm long, filiform; sepals ovate, hairy along mid-line outside, glabrous inside; petals linear or oblong, c. 2.5 by 1.5 mm, glabrous, orange-yellow; disc 5 glands; stamens 3, staminal column c. 0.5 mm long, anthers 0.3-0.5 mm long. Pistillate inflorescences stout, subterminal, few-flowered, up to 15 cm long; bracts ovate or elliptic, 11-25 by 3.5-4 mm, foliaceous, sparsely hairy. Pistillate flowers: pedicel c. 13 mm long, sparsely hairy; sepals linear or oblong, 1-1.5 by 0.5-1 mm; petals obovate, 1.5-2 by 1-1.5 mm, orange-yellow; disc glands 5; ovary glabrous; style 0.2-0.3 mm long. Fruits: pedicel 1.5-2.5 cm long, capsule 1-1.5 cm diam., glabrous. Seeds trigonous, 7-9 by 6-7 mm.

    Thailand.— PENINSULAR: Surat Thani (Ko Samui), Phuket (Thalang), Satun (Tarutao), Songkhla (Padang Besar, Saba Yoi), Pattani (Khao Kala Khiri), Yala (Banang Sta), Narathiwat (Bachow).

    Distribution.— India (Andaman Is.), Malay Peninsula, Banka (type), Java.

    Ecology.— In evergreen forest or on limstone hills. Altitude: Sea level up to 220 m.

3. Trigonostemon capillipes (Hook.f.) Airy Shaw, Kew Bull. 20: 413. 1966; Kew Bull. 26: 145. 1972; Whitmore, Tree Fl. Malaya 2: 134. 1973; Milne, Kew Bull. 50: 45. 1995; Chantar., Thai Forest Bull. (Bot.) 33: 24. 2005; in Welzen & Chayamarit, Fl. Thailand 8, 2: 576. 2007. — Dimorphocalyx capillipes Hook.f., Fl. Brit. Ind. 5: 404. 1888; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.iii: 33. 1911; Ridl., Fl. Malay Penins. 3: 266. 1924.

Shrubs up to 3.5 m high; branchlets puberulous. Stipules triangular, 1.1-2.3 mm long. Leaves: petiole (0.5-)1-2 cm long, puberulous, glabrescent; blade obovate, 9.3-20 by 3-7 cm, membranous to chartaceous, glabrescent; base rounded or obtuse, margin shallowly and distantly crenate-dentate, apex shortly caudate or acuminate-obtuse; venation triplinerved, nerves in 9-14 pairs. Staminate inflorescences cauliflorous, slender, branched. Staminate flowers: pedicel c. 1 cm long; sepals obovate, oblong or ovate-oblong, c. 2.5 by 2 mm, sparsely hairy on the back; petals obovate, c. 2 by 1.5 mm; disc cupular, 5-lobed; stamens 3, staminal column c. 0.5 mm long; anthers c. 0.1 mm long. Pistillate inflorescences almost simple, slender, axillary, few-flowered, up to 6 cm long. Pistillate flowers: pedicel 9-10 mm long, elongate, sepals unequal, 2 larger, 4.7-5 by c. 2 mm, 3 smaller, 3.7-3.8 by c. 1.5 mm, sparsely hairy outside, glabrous inside, rim membranous, fimbriate; petals oblong elliptic, c. 1.8 by 1 mm, purplish red or red; dics cupular, 5-lobed; ovary puberulous; style c. 0.8 mm long. Fruits: pedicel c. 1 cm long; capsule globose, 16-21 by 4-7 mm, minutely adpressed puberulous with an accrescent calyx.

    Thailand.— SOUTH-EASTERN: Chanthaburi (Khao Soi Dao); SOUTH-WESTERN: Uthai Thani (Katatak); PENINSULAR: Ranong (Khao Pawta Chong Dong, Khao Pawta Luang Khieo), Nakhon Si Thammarat.

    Distribution.— Malay Peninsula (Singapore type), Borneo.

    Ecology.— In evergreen forest. Altitude: 10-900 m.

4. Trigonostemon heterophyllus Merr., Lingnan. Sc. Journ. 9: 38. 1930; Chantar., Thai Forest Bull. (Bot.) 33: 24. 2005; in Welzen & Chayamarit, Fl. Thailand 8, 2: 577, Plate XXXI: 1. 2007.

Shrubs up to 1 m high, branchlets terete, hairs dense, ferrugineous. Stipules caducous. Leaves: petiole 3-6 mm long, densely ferrugineous; blade obovate, 10-35 by 4-7 cm, membranous to chartaceous, base obtuse, margin ciliate and strongly denticulate, apex acuminate; nerves in 10-15 pairs.. Inflorescences racemose, axillary, up to 2.5 cm long, few-flowered, ciliate; bracteoles elliptic or falcate, acuminate, ciliate, 10-15 by 4-5 mm. Staminate flowers: sepals ovate or oblong elliptic, 3 larger c. 2.5 mm long; 2 smaller c. 1.5 mm long, margin ciliate; petals ovate or elliptic, c. 4 by 2.5 mm; disc glands 5; stamens 3, staminal column c. 0.5 mm long, anthers c. 0.5 mm long. Pistilate flowers: pedicel short; solitary; sepals elliptic, c. 5 mm long, apex long ciliate acuminate; petals elliptic or obovate, 4.5-5 by c. 4 mm, glabrous, purplish; disc glands 5, oblong; style c. 1 mm long. Fruits and seeds unknown.

    Thailand.— NORTH-EASTERN: Nong Khai (Phu Wua).

    Distribution.— China (type), Laos.

    Ecology.— In light evergreen forest, 200-400 m.

5. Trigonostemon kerrii Craib, Bull. Misc. Inform., Kew 1924: 97. 1924; Gagnep. in Lecomte, Fl. Indo-Chine 5: 321. 1925; Chantar., Thai Forest Bull. (Bot.) 33: 25. 2005; in Welzen & Chayamarit, Fl. Thailand 8, 2: 577. 2007.

Shrubs up to 4 m high; branchlets terete or angled, hirsute, glabrescent. Stipules triangular or elliptic, c. 2 mm long. Leaves: petiole (0.3-)1.5-3(-3.8) cm long, glabrescent; blade narrowly elliptic or obovate, 8-20 by 2.4-5 cm, (thinly) chartaceous, sparsely hairy, glabrescent, base cuneate, margin minutely denticulate, apex obtuse-acuminate; venation penninerved, nerves in 8-16 pairs. Staminate inflorescences racemose, axillary, up to 8 cm long, short adpressed pilose; bracteoles c. 3 mm long. Staminate flowers: pedicel 6-10 mm long, glabrous or sparsely hairy; sepals obovate, 1.5-2 by 1.2-1.5 mm, adpressed pilose outside; petals obovate or rotund-obovate, c. 3.5 by 2.5 mm, dull red; disc glands 5; stamens 3, staminal column c. 1.5 mm long, anthers c. 0.5 mm long. Pistillate inflorescences racemose, axillary, up to 17 cm long; bracteoles ovate or obovate, 4.3-5.6 by 0.8-1.5 mm, hairy outside, glabrous inside. Pistilate flowers: pedicel 1.5-2.5 mm long; sepals: margin fringed with elongate capitate glands; petals ovate or oblong, 4.3-5 by c. 2 mm, hairy on the mid-line outside, glabrous inside, dull red; disc glands 5; ovary glabrous; style c. 0.5 mm long. Fruits: pedicel 1.5-3 mm long; capsule c. 7 mm in diameter, with a persistent calyx. Seeds globose, 5-6 mm in diameter.

    Thailand.— NORTHERN: Tak, Phitsanulok (Nakhon Thai-KERR 5871, lectotype BK, isolectotypes BM, K, TCD).

    Distribution.— Endemic.

    Ecology.— In evergreen or mixed forest. Altitude: 100-200 m.

6. Trigonostemon laevigatus Müll.Arg., Flora 47: 538. 1864; in DC., Prodr. 15, 2: 1111. 1866; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.iii: 94. 1911; Ridl., Fl. Malay Penins. 3: 265. 1924; Jablonski, Brittonia 15: 167. 1963; Chantar., Thai Forest Bull. (Bot.) 33: 25. 2005; in Welzen & Chayamarit, Fl. Thailand 8, 2: 578, Fig. 93. 2007. — Trigonostemon anomalus Merr., Philipp. J. Sci. 16: 569. 1920; Enum. Philip. 2: 451. 1923. — Trigonostemon petelotii Merr., Univ. Calif. Publ. Bot. 10: 425. 1924. — Trigonostemon laevigatus Müll.Arg. var. petiolaris Airy Shaw, Kew Bull. 32: 417. 1978.

Shrubs or small trees up to 5 m high; branchlets terete, pubescent. Stipules triangular, 1-1.5 mm long. Leaves subopposite; petiole 0.3-1(-1.5) cm long, sparsely hairy, glabrescent, ribbed; blade ovate to obovate, 8.4-15(-23.7) by 3-8(-9.1) cm; thinly chartaceous; base broadly cuneate or obtuse, margin entire, slightly undulate, apex acute to cuspidate, very apex blunt; venation triplinerved, nerves in 7-10 pairs. Inflorescences cymose, axillary, 4-4.5 cm long. Staminate flowers pedicel c. 2 mm long, glabrous; sepals outer 3 smaller, ovate, 1.3-1.5 by 0.8-1, hairy outside; petals ovate, 3-3.2 by 2.5-2.7, yellowish; stamens 3, staminal column very short, c. 0.1 mm long, anthers 0.3-0.4 mm long. Pistillate flowers: pedicel 1.5-2 cm long; sepals oblong, 1.4-1.4 by 0.7-0.9; petals elliptic, 1.5-2 by 1-1.5 mm, yellowish; disc annular; ovary hairy, style c. 0.1 mm long. Fruits: pedicel 3.5-4.5 cm long; capsule globose, axis 6-7 mm long. Seeds trigonous, 6-7 by c. 5 mm.

    Thailand.— PENINSULAR: Ranong (Khao Pawta Luang Khieo), Nakhon Si Thammarat (Khiriwong), Satun (Tarutao), Narathiwat (Sungei Kolok).

    Distribution.— Myanmar, Indo-China, Malay Peninsula, Borneo (Kalimantan-type), Philippines.

    Ecology.— In evergreen forest. Altitude: 50-1,300 m.

7. Trigonostemon longifolius Baill., Étude Gén. Euphorb.: 341.1858; Müll.Arg. in DC., Prodr. 15, 2: 1108. 1866; Hook.f., Fl. Brit. Ind. 5: 396. 1887; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.iii: 88, f. 28. 1911; Ridl., Fl. Malay Penins. 3: 264. 1924; Jablonski, Brittonia 15: 162. 1963; P.H.HÔ, Câyco Viêtnam 2(1): 341. 1992; Chantar., Thai Forest Bull. (Bot.) 33: 26. 2005; in Welzen & Chayamarit, Fl. Thailand 8, 2: 579, Fig. 94. 2007.

Shrubs or small trees up to 5 m high; branchlets ribbed, pubescent. Stipules triangular, 0.7-3 mm long. Leaves: petiole 1-2 cm long, densely pubescent; blade narrowly obovate or spathulate, 22-55 by 3-15 cm, chartaceous, glabrous above, pubescent beneath; base long attenuate, margin serrate, apex caudate-acuminate; venation penninerved, nerves in 16-25 pairs. Inflorescences spicate, axillary, uni- or bisexual, up to 28 cm long, hirsute; bracteoles linear or subulate, c. 2.5 by 0.3-0.4 mm, setose or hairy outside, glabrous inside. Staminate flowers: pedicel 1.5-2.5 mm long; sepals oblong, 1.8-2.5 by 1-1.4 mm, hairy on the mid-line outside, glabrous inside; petals ovate, 1.5-2 by c. 1.5 mm, glabrous, dark purple; disc glands 5; stamens 3 with large appendages, staminal column 1-1.3 mm long, anthers 0.6-0.7 mm long. Pistillate flowers: pedicel 3.7-4.5 mm long; sepals elliptic, c. 2.5 by 1.2-1.3 mm, hairy outside, glabrous inside; petals broadly obovate, 2.8-3 by 2.1-2.3 mm; disc annular, ovary hirsute; styles c. 0.1 mm long. Fruits: pedicel 4-6mm; capsule depressed globose, c. 1 cm in diameter, axis 7-8 mm long, hairy. Seeds trigonous, 7-8 by 4-5 mm.

    Thailand.— SOUTH-EASTERN: Chanthaburi; PENINSULAR: Ranong (Khao Pawta Chong Dong, Klong Naka), Krabi (Nong Chik), Nakhon Si Thammarat (Khao Luang, Tasala), Phuket, Phatthalung (See Bahn Pote), Satun (Knan Kalong, Kuan Po), Pattani, Yala (Banang Sta), Narathiwat (Waeng).

    Distribution.— Myanmar, Malay Peninsula (type), Indonesia (Sumatra).

    Ecology.— In evergreen forest. Altitude: 50-1,600 m.

    Vernacular.— Thao yaai mom paa (เท้ายายม่อมป่า), Aaibaao (อ้ายบ่าว) (Pattani).

8. Trigonostemon murtonii Craib, Bull. Misc. Inform., Kew 1911: 464. 1911 (‘murtoni’); Pax & K.Hoffm. in Engler., Pflanzenr. IV.147.vi: 128. 1912; P.H.HÔ, Câyco Viêtnam 2(1): 342. 1992; Chantar., Thai Forest Bull. (Bot.) 33: 26. 2005; in Welzen & Chayamarit, Fl. Thailand 8, 2: 581. 2007. — Trigonostemon pinnatus Gagnep., Bull. Soc. Bot. France 64: 752. 1923; in Lecomte, Fl. Indo-Chine 5: 318. 1925.

Shrubs or small trees 1-2 m high; branchlets terete, strigose, glabrescent. Stipules triangular, c. 0.7 mm long. Leaves pseudo-verticillate; petiole 3-7 mm long, glabrescent; blade obovate or oblong-obovate, 7.5-14.2 by 2.3-4 cm, chartaceous, glabrous and shining above, strigose along midrib beneath, base obtuse or truncate, margin slightly denticulate, apex shortly and bluntly acuminate or obtuse; venation penninerved, nerves in 13-17 pairs; hairy, glabrescent. Inflorescences racemose, axillary, up to 5 cm long, pubescent; bracteoles ovate, 5.5-8.5 by 1-2 mm long, obovate or narrowly elliptic, hairy outside, sparsely hairy inside, glabescent. Staminate flowers: pedicel 3.5-4 mm long; sepals linear or elliptic, 1.8-2 by 0.6-0.7 mm, hairy outside, glabrous inside; petals oblong-obovate, 3.5-3.7 by 1.7-1.8 mm, sparsely ciliate on both sides, purplish-red; disc glands 5; stamens 3, staminal column c. 0.6 mm long, anthers 0.25-0.35 mm long. Pistillate flowers: pedicel 4-6 mm long; sepals elliptic, 5-8 by 1-2 mm, pubescent outside, glabrous inside; petals elliptic or obovate oblong, 2-3 by c. 1.5 mm, hairy; disc glands 5; ovary pubescent; style minute. Fruits and seeds unknown.

    Thailand.— SOUTH-EASTERN: Trat (Klong Yai, Ko Klone, MURTON 18 - holotype K).

    Distribution.— Vietnam (Cochinchina).

    Ecology.— In shaded and rocky area.

9. Trigonostemon pachyphyllus Airy Shaw, Kew Bull. 25: 546. 1971; Chantar., Thai Forest Bull. (Bot.) 33: 27. 2005; in Welzen & Chayamarit, Fl. Thailand 8, 2: 581. 2007.

Shrubs up to 1.5 m high; branchlets ribbed, pilose, glabrescent. Stipules subulate, 0.6-0.8 mm long. Leaves: petiole 5-25 mm long, blade narrowly elliptic or obovate, 12-26 by 3-6.5 cm, glabrous above, pilose beneath, base truncate or rounded, margin revolute, minutely denticulate, apex subobtuse to acuminate; venation penninerved, nerves in 11-17 pairs. Inflorescences abbreviated, up to 4 cm long; bracteoles obovate or spathulate, 3-3.8 by 0.7-1 mm, hairy outside, glabrous inside. Staminate flowers: pedicel 4.3-4.5 mm long; sepals ovate, 1.8-2 by 1.7-1.8 mm, hairy outside, glabrous inside, rim fimbriate; petals obovate, 6.2-6.3 by c. 2.5 mm; disc glands 5, spathulate; stamens 5, staminal column c. 2 mm long, anthers 0.5-0.8 mm long. Pistillate flowers: pedicel 4-10 mm long; sepals ovate to elliptic, 5-6 by 2-3 mm; petals oblong, 8-10 by 3-4 mm, hairy outside, glabrous inside, red; disc glands 5, spathulate; ovary tomentose; style c. 2.5 mm long. Fruits and seeds unknown.

    Thailand.— SOUTH-EASTERN: Chanthaburi (Khao Soi Dao, KERR 19429 -holotype K); PENINSULAR: Narathiwat (Waeng).

    Distribution.— Endemic.

    Ecology.— In evergreen forest. Altitude: 300-700 m.

10. Trigonostemon phyllocalyx Gagnep., Bull. Soc. Bot. France 69: 753. 1923; in Lecomte, Fl. Indo-Chine 5: 312. 1925; P.H.HÔ, Câyco Viêtnam 2(1): 341. 1992; Chantar., Thai Forest Bull. (Bot.) 33: 27. 2005; in Welzen & Chayamarit, Fl. Thailand 8, 2: 581. 2007.

Small trees up to 6 m high; branchlets pubescent. Stipules triangular, 1.7-2.8 by 2.2-3.5 mm. Leaves: petiole (0.5-)4.5-10 cm long, pubescent, glabrescent; blade ovate or elliptic, (7-)12.5-26 by (2-) 4.5-6 cm, chartaceous; base obtuse or rounded, margin minutely denticulate, apex acuminate; glabrous above, glabrous to very thinly pubescent beneath; venation triplinerved, nerves in 9 or 10 pairs. Inflorescences paniculate, axillary, up to 8 cm long, pubescent; bracteoles linear or oblong, 3-5 mm long. Staminate flowers: pedicel c. 3 mm long, finely puberulous; sepals ovate, 1.5-2.1 by 2.5-2.9 mm, rim fimbriate; petals ovate, 3-3.2 by 2.8-3 mm; disc annular; stamens 3, staminal column c. 0.3 mm long, anthers c. 0.7 mm long. Pistillate flowers: pedicels c. 10 mm long; sepals ovate, 5-8 by 1-1.2 mm, subcordate at base, with 3 parallel median nerves, finely and sparsely pilose; petals 5, ovate, 1-5 mm long, rim ciliate; disc annular; ovary finely puberulous; style c. 0.6 mm long. Fruits: pedicel c. 10 mm long; capsule smooth, finely puberulous, c. 12 mm long, with an accrescent calyx, c. 17 mm long. Seeds globose, 7-8 mm in diameter.

    Thailand.— SOUTH-EASTERN: Chanthaburi (Khao Sabap, Pliew waterfall).

    Distribution.— Vietnam (Annam-type).

    Ecology.— In evergreen forest. Altitude: c. 200 m.

11. Trigonostemon quocensis Gagnep., Bull. Soc. Bot. France 69: 753. 1923; in Lecomte, Fl. Indo-Chine 5: 316. 1925; P.H.HÔ, Câyco Viêtnam 2(1): 343. 1992; Chantar., Thai Forest Bull. (Bot.) 33: 27. 2005; in Welzen & Chayamarit, Fl. Thailand 8, 2: 582. 2007.

Shrubs or small trees up to 7 m high; branchlets terete, sparsely hairy or glabrescent. Stipules triangular, c. 1 mm long. Leaves: petiole (1-)1.5-4(-5.7) cm long, sparsely hairy; blade broadly elliptic-oblong, (7.5-)10-20(-28) by (2.8-)4-7.5(-8.5) cm, chartaceous, base rounded or broadly cuneate, with 2 glands at insertion, margin entire with sparse hairs, apex acuminate to caudate; venation triplinerved, pubescent, glabrescent, nerves in 5-12 pairs. Inflorescences paniculate, axillary, up to 32 cm long, pubescent; peduncle 1-6 cm long; bracteoles narrowly oblong, 7-10 by 0.6-1.2 mm. Staminate flowers: pedicel 3.7-5 mm long; sepals ovate, 1.7-2.2 by 1.2-1.5 mm, sparsely hairy outside, rim fimbriate; petals obovate, c. 3 by 1.5 mm, glabrous, yellow; stamens 3, staminal column c. 1 mm long, anthers c. 0.4 mm long. Pistillate flowers: pedicel 5-15 mm long; sepals ovate, 1.8-3.1 by 0.8-1.5 mm, hirsute outside; petals oblong, 2.5-3.7 by 1.8-2.1 mm, yellow; disc annular; ovary pubescent; style c. 0.7 mm long. Fruits: pedicel 1.5-2 cm long; capsule depressed globose, c. 1 cm in diameter, thinly adpressed pubescent. Seeds globose, 7-8 mm in diameter.

    Thailand.— EASTERN: Nakhon Ratchasima (Katok, Pak Thongchai, Sikhiu); SOUTH-WESTERN: Prachuap Khiri Khan; SOUTH-EASTERN: Chanthaburi (Khao Soi Dao Nua); PENINSULAR: Ranong (Khao Pawta Chong Dong), Surat Thani (Khao Wong, Khiriratnikom), Phangnga (Khao Nang Hong, Trap Put), Nakhon Si Thammarat, Phatthalung (Klong Hui Kao).

    Distribution.— Myanmar, Indo-China (Cambodia type).

    Ecology.— In evergreen forest. Altitude: 50-630 m.

12. Trigonostemon reidioides (Kurz) Craib, Bull. Misc. Inform., Kew 1911: 464. 1911; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.vi: 128. 1912; Gagnep. in Lecomte, Fl. Indo-Chine 5: 316. 1925; P.H.HÔ, Câyco Viêtnam 2(1): 343. 1992; Chantar., Thai Forest Bull. (Bot.) 33: 28. 2005; in Welzen & Chayamarit, Fl. Thailand 8, 2: 582, Fig. 95, Plate XXX: 3. 2007. — Baliospermum reidioides Kurz, Flora 58: 32. 1875; For. Fl. Brit. Burma 2: 411. 1877; Hook.f., Fl. Brit. Ind. 5: 461. 1887; Williams, Bull. Herb. Boiss. Ser. 2,5: 32. 1905; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.vi: 29. 1912.

Shrubs up to 1.5 m high, branchlets pubescent, glabrescent. Stipules triangular, 0.8-1 mm long. Leaves: petiole 0.8-1.9 cm long, sparsely hairy; blade narrowly or broadly ovate to obovate, 5.5-12 by 1.1-4 cm, chartaceous, hairy on both sides, base obtuse, margin glandular serrulate, apex acute or acuminate; venation triplinerved, nerves in 8-12 pairs. Inflorescences racemose, axillary, 9-14 cm long. Staminate flowers: pedicel 1-2 cm long; sepals obovate, 2-3 by 1-2 mm, hairy outside; petals obovate, 4-5 by 2-3 mm, dark red; disc cupular, undulate; stamens 3, staminal column 1-1.5 mm long, anthers 0.5-0.8 mm long. Pistillate flowers: pedicel 0.8-1.5 mm long; sepals 5, oblong, 2-5 by 1-1.5 mm, sparsely hairy outside; petals 5, obovate, 4-5 by 1-2 mm, dark red; disc cupular; ovary pubescent; style c. 0.5 mm long. Fruits: pedicel c. 1.5-3.5 cm long; capsule globose, pubescent, 1-1.4 cm in diameter. Seeds globose, 5-6 mm long.

    Thailand.— NORTHERN: Tak (Ban Na, Doi Muser), Sukhothai (Khao Luang), Phitsanulok (Thung Salang Luang); NORTH-EASTERN: Phetchabun, Loei (Wang Sapung), Udon Thani, Nong Khai (Bung Khla, Dong Srichompoo, Phon Phisai, Seka), Sakon Nakhon (Phu Phan, Wa Nawn), Nakhon Phanom (Phu Langka), Kalasin, Maha Sarakham (Ban Ta Yae, Kosumpisai), Khon Kaen (Tha Phra); EASTERN: Chaiyaphum, Nakhon Ratchasima (Bua Yai, Khao Yai), Buri Rum (Nang Rong), Surin (Sangka), Si Sa Ket (Kantharom), Ubon Ratchathani (Phu Jong Nayoy National Park); SOUTH-WESTERN: Uthai Thani (Huay Ka Kang), Kanchanaburi (Khao Thong, Wang Kanai, TEYSMANN 5981, isotype K), Phetchaburi (Cha-am), Ratchaburi, Prachuap Khiri Khan (Nong Kae); SOUTH-EASTERN: Sa Kaeo (Aranya Prathet), Prachin Buri, Chon Buri (Sriracha), Rayong (Ban Chak Done), Chanthaburi (Makham), Trat (Klong Yai, Takam).

    Distribution.— Indo-China.

    Ecology.— In open dry dipterocarp forest. Altitude: Sea level up to 1,100 m.

    Vernacular.- Khaao yen noen (ข้าวเย็นเนิน) (Ratchaburi, Prachuap Khiri Khan); Duu bia (ดู่เบี้ย), Duu tia (ดู่เตี้ย) (Phetchaburi); Thanong, Rak thanong (รักทะนง) (Nakhon Ratchasima); Tha nong daeng (ทะนงแดง) (Prachuap Khiri Khan); Naanng saeng (นางแซง) (Ubon Ratchathani); Lot thanong (โลดทะนง) (Ratchaburi, Prachin Buri, Trat); Lot thanong daeng (โลดทะนงแดง) (Buriram); Naat kham (หนาดคำ) (Northern); Hua yaa khaao yen noen (หัวยาข้าวเย็นเนิน) (Ratchaburi).

    Uses.— Roots applied for emetic, anti-asthmatic medicine and as laxative.

13. Trigonostemon thyrsoïdeus Stapf, Bull. Misc. Inform., Kew 1909: 264. 1909 (‘thyrsoideum’); P.H.HÔ, Câyco Viêtnam 2(1): 344. 1992; Chantar., Thai Forest Bull. (Bot.) 33: 29. 2005; in Welzen & Chayamarit, Fl. Thailand 8, 2: 584, Plate XXXII: 1. 2007.

Shrubs or small trees up to 6 m high; branchlets sparsely hairy, glabrescent. Stipules triangular, c. 1 mm long. Leaves: petiole very variable in length, (2.5-)7.5-14 cm long, sparsely hairy; blade elliptic to obovate to oblong, (10.5-)13-24 by 3.5-9.5 cm, membranous or thinly chartaceous, glabrous on both sides, base cuneate or subobtuse, margin broadly, distantly and shallowly crenate, apex acute to caudate; venation triplinerved, sparsely hairy, glabrescent, nerves in 9-15 pairs. Inflorescences pyramidal thyrsoid, terminal, up to 20 cm long, adpressed puberulous, branches angled or flattened. Staminate flowers: pedicel 2-5 mm long; sepals ovate-elliptic, c. 1.5 by 1 mm, pubescent outside, margin membranous; petals oblong, 3-3.5 by 1.8-2 mm, glabrous, yellow; disc glands 5, obovate-oblong; stamens 5, c. 1.5 mm long, staminal column minute, c. 1 mm long, anthers c. 0.25 mm long, with appendage up to 0.25 mm long. Pistillate flowers: pedicel 3.5-4 mm long; sepals ovate-elliptic, c. 1.5 by 0.8-1 mm long, pubescent outside, margin membranous; petals oblong, c. 4 mm by 1-1.5 mm, glabrous, yellow; disc glands 5; ovary glabrous; style c. 0.1 mm long. Fruits: pedicel 2.7-4.2 cm; capsule 1.2-1.5 cm in diameter, sparsely and shortly aculeate. Seeds slightly globose, 6-7 mm in diameter.

    Thailand.— NORTHERN: Mae Hong Son, Chiang Mai (Doi Chiangdao, Doi Inthanon), Chiang Rai (Khunkorn waterfall), Nan (Ban Pa Gum, Doi Phu Kha National Park), Phrae (between Pha Tuem and Ban Phra).

    Distribution.— Myanmar, China (Yunnan: type), Laos, Vietnam.

    Ecology.— In evergreen or pine-dipterocarp forest. Altitude: 600-1,500 m.

14. Trigonostemon verticillatus (Jack) Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.iii: 87. 1910; Jablonski, Brittonia 15: 164. 1963; Chantar., Thai Forest Bull. (Bot.) 33: 30. 2005; in Welzen & Chayamarit, Fl. Thailand 8, 2: 585, Plate XXXI: 2. 2007. — Enchidium verticillatum Jack, Malayan Misc. 2: 90. 1822; Comp. Bot. Mag. 1: 257. 1836 (excl. syn. Rumph.); Müll. Arg. in DC., Prodr. 15, 2: 1256. 1866; Merr., J. Arnold Arb. 33: 224. 1952. — Telogyne indica Baill., Étude Gén. Euphorb.: 238. 1858. — Trigonostemon indicus (Baill.) Müll.Arg., Linnaea 34: 214. 1865; in DC., Prodr. 15, 2: 1107. 1866; Hook.f., Fl. Brit. Ind. 5: 398. 1887; Ridl., Fl. Malay Penins. 3: 264. 1924.

Shrubs or small trees up to 6 m high; branchlets terete or ribbed, glabrescent. Stipules triangular, 1-2 mm long. Leaves crowded towards the tips of the branchlets; petiole (1.5-)4-13(-20) cm long, glabrous; blade ovate-elliptic or narrowly elliptic, 12-33 by 2.5-8.5 cm, chartaceous to coriacceous, glabrous; base rounded or cuneate, margin entire, apex acuminate; venation penninerved; nerves in 9-21 pairs. Inflorescences simple, narrowly pseudo-racemose, axillary, up to 20 cm long, glabrous or puberulous; bracteoles linear or ovate, 1.2-1.3 by c. 0.5 mm, hairy. Staminate flowers: pedicel 1.2-1.3 mm long; sepals ovate, c. 2 by 1.6 mm, margin fimbriate; petals ovate-spathulate, 3-3.2 by 2.2-3 mm, margin fimbriate, glabrous, dark purple; disc annular; stamens 5, staminal column 1.1-1.2 mm long, anthers 1-1.2 mm long. Pistillate flowers: pedicel 2-3 mm long; sepals ovate, c. 2 by 1.5 mm; petals ovate to elliptic, c. 3 by 2.5 mm,, dark purple; disc urceolate; ovary velutinous; style c. 0.6 mm long. Fruits: pedicel 2-3.5 mm long; capsule glabrous, c. 1 cm in diameter, axis 3.5-4 mm long, usually finely and very shortly velutinous, rarely glabrous. Seeds globose, 4.5-6 mm in diameter.

    Thailand.— SOUTH-EASTERN: Chanthaburi (Phliu waterfall, Khao Sabap); PENINSULAR: Ranong (Kam Puam, Klong Naka), Phangnga (Ko Yao Yai, Takuapa), Narathiwat (Sukhirin).

    Distribution.— Malaysia, Sumatra (type).

    Ecology.— In evergreen forest. Altitude: Sea level up to 300 m.