Flora of Thailand
Euphorbiaceae
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Blume, Bijdr.: 621. 1825; Airy Shaw, Kew Bull. 26: 341. 1972; G.L.Webster, Ann. Missouri Bot. Gard. 81: 91. 1994; Welzen, Blumea 43: 145; Radcl.-Sm., Gen. Euphorbiacearum: 238. 2001; Welzen in Welzen & Chayam., Fl. Thailand 8, 2: 557. 2007; G.L.Webster in Kubitzki, Fam. Gen. Vasc. Pl. 11: 129. 2014.— Polydragma Hook.f., Hook. Ic. Pl. 18: pl. 1701. 1887; Fl. Brit. Ind. 5: 456. 1888.
Shrubs to trees, monoecious. Indumentum of simple hairs. Stipules early caducous. Leaves alternate, simple; petiole basally and apically pulvinate; blade papery, symmetric, base rounded to cuneate, with 2 or 3 (confluent) glands in margin at each side (small black dots), margin entire, usually green when dry, paler below, nerves looped and joined near margin, veins scalariform, quaternary veins more reticulate. Inflorescences axillary to pseudoterminal racemes, usually one per axil, with staminate or pistillate flowers, pendulous when staminate, erect when pistillate; flowers single per node. Flowers actinomorphic, petals and disc absent. Staminate flowers sessile to shortly pedicelled; sepals 3; stamens more than 100, united into 4-7 bifurcating androphores; pistillode absent. Pistillate flowers pedicelled; sepals 3+3; ovary 3-locular, one ovule per locule; style absent, stigmas 3, not split. Fruits lobed capsules, outside smooth, glabrous (Thailand), septicidally breaking into 3 bivalved parts. Seeds obovoid, without arilloid.
Two species, one endemic in Peninsular Thailand, the other one ranging throughout Malesia from the Malay Peninsula to Papua New Guinea, though absent from Sumatra. Classification: Subfam. Acalyphoideae, tribe Acalypheae, subtribe Lasiococcinae.
Spathiostemon moniliformis Airy Shaw, Kew Bull. 16: 357. 1963; Kew Bull. 20: 408. 1967; Kew Bull. 26: 341. 1972; Hook. Icon. Pl. 38: tab. 3720. 1974; Welzen, Blumea 43: 150, fig. 4 i-k, map 3. 1998; in Welzen & Chayam., Fl. Thailand 8, 2: 557, Fig. 83. 2007.— Spathiostemon forbesii non Airy Shaw: Airy Shaw 36: 345. 1981, pro Thai specimens.
Shrubs to trees up to 10 m high. Stipules 1-2.4 by 0.8-1.1 mm. Leaves: petiole 1.3-2.8 cm long, glabrous; blade (somewhat ovate to) elliptic, 6.2-26.5 by 2.3-9.5 cm, length/width ratio 1.8-2.7, apex cuspidate to caudate, the tip rounded to acute and mucronulate, smooth and glabrous on both sides, venation sunken (to raised) above, raised beneath with 4-6 pairs of nerves, domatia absent. Inflorescences (sub)glabrous, staminate ones 6-28 cm long; pistillate ones up to 3.3 cm long. Flowers white to yellowish; bracteoles in staminate flowers spreading and cordate, forming cup. Staminate flowers sessile; sepals ovate to elliptic, 2.4-2.5 by 1.8-2 mm; stamens: androphores and filaments up to 5 mm long, anthers c. 0.4 by 0.3 mm. Pistillate flowers: pedicel c. 0.3 mm long; sepals ovate, outer c. 1.7 by 1.8 mm, thick, keeled, inner c. 1.1 by 1.3 mm, thinner; pistil c. 0.8 by 0.6 mm, smooth, glabrous. Fruits c. 9 by 6 mm, reddish to dark brown. Seeds c. 4.8 by 4 mm.
T h a i l a n d.— SOUTH-WESTERN: Prachuap Khiri Khan (Bang Saphan); PENINSULAR: Chumphon (Langsuan, Ta Ngao), Ranong (Kraburi, Lam Hiang), Surat Thani (Ban Krut, Bang Bao, Khao Rahu, Khao Rak, Khao Tha Phet, Surat Thani, Tachang), Krabi (Khao Na Wua), Phuket (Kraburi).
D i s t r i b u t i o n.— Endemic in Peninsular Thailand (type: Ban Krut, Surat Thani, KERR 18162, holotype K).
(squares; dots in Malesia: Spathiostemon javensis Blume)
E c o l o g y.— Often common in evergreen and secondary forest with evergreen patches. Altitude: 10-200 m.
V e r n a c u l a r.— Ka lai (กาไล), kha khao (ค่าขาว), khan laen (แคนแลน), khat lai (คัดไล), kra duk chang (กระดูกช้าง) (Peninsular).