Flora of Thailand



63. Microstachys


H.-J. Esser & P.C. van Welzen


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Genus description

Species description




A.Juss., Euph. Gen.: 48, t. 15, fig. 50. Feb. 1824; G.L.Webster, Ann. Missouri Bot. Gard. 81: 122. 1994; Esser, Kew Bull. 53: 957. 1998; Blumea 44: 175. 1999; in Radcl.-Sm., Gen. Euphorbiacearum: 365. 2001; Esser & Welzen in Welzen & Chayam., Fl. Thailand 8, 2: 452. 2007; G.L.Webster in Kubitzki, Fam. Gen. Vasc. Pl. 11: 196, Fig. 43. 2014Cnemidostachys Mart. & Zucc., Flora 7.1 Beibl. 4: 136. 1824.— Elachocroton F.Muell., Hook. J. Bot. Kew Gard. Misc. 9: 17. 1857.— Stillingia sect. Cnemidostachys (Mart. & Zucc.) Baill., Ιtude Euphorb.: 515. 1858.— Stillingia sect. Elachocroton (F.Muell.) Baill., Ιtude Euphorb.: 517. 1858.— Sebastiania sect. Microstachys (A.Juss.) Mόll.Arg. in DC., Prod. 15, 2: 1166. 1866.— Excoecaria sect. Cnemidostachys (Mart. & Zucc.) Baill., Adansonia 6: 323. 1867.— Sapium sect. Sebastiania (Spreng.) T.Post & Kuntze subsect. Microstachys (A.Juss.) T.Post & Kuntze, Lex. Gen. Phan.: 498. 1903.— Sebastiania sect. Elachocroton (F.Muell.) Pax in Engl., Pflanzenr. IV.147.v: 114. 1912.— Sebastiania sect. Cnemidostachys (Mart. & Zucc.) G.L.Webster, J. Arnold Arbor. 48: 386. 1967.


Woody herbs to subshrubs, monoecious; stem with longitudinal rims. Indumentum simple hairs, rarely absent. Stipules triangular, undivided or apically divided into several ciliae. Leaves regularly alternate, simple, symmetric; blade ovate to elliptic to linear, base glandless, margin with very dense, minute glandular teeth, often nearly touching, apex rounded to mucronate, lower surface at base often with few marginal to submarginal glands, secondary nerves arching and usually looped, indistinct, veins indistinct. Inflorescences terminal and axillary, spike-like thyrses, yellowish, unbranched, pistillate and staminate flowers in same thyrse or pistillate flowers separated; bracts of staminate cymules with a pair of glands touching the axis of the thyrse. Flowers symmetric, sepals 3-merous, petals and disc absent. Staminate flowers 1–3 together, with very short pedicel; stamens 3, filaments longer than anthers; pistillode absent. Pistillate flowers 1(2) at base of staminate thyrse or often separated from staminate part, sessile; sepals glandless or with a pair of minute basal glands; ovary 3-locular, ovules 1 per locule, each carpel usually with 2 longitudinal rows of spines. Fruits oblong capsules, usually with 6 rows of spines. Seeds with a large persistent caruncle.

    Seventeen species currently accepted, 15 of them in tropical South America south of the Amazon, one in northern South America and Central America up to Mexico, and one in the Old World from Africa through Asia to N Australia, throughout Thailand and Malesia except the Philippines, and New Guinea. Three additional African species will have to be attributed to Microstachys. Classification: Subfam. Euphorbioideae, tribe Hippomaneae, subtribe Hippomaninae.


Microstachys chamaelea (L.) Mόll.Arg., Linnaea 32: 95. 1863; Esser, Blumea 44: 176, fig. 4, map 4. 1999; Esser & Welzen in Welzen & Chayam., Fl. Thailand 8, 2: 453, Fig. 46, Plate XXII: 3. 2007Tragia chamaelea L., Sp. Pl.: 981. 1753.— Cnemidostachys chamaelea (L.) Spreng., Syst. Veg. 3: 835. 1826.— Elachocroton asperococcus F.Muell., Hook. J. Bot. Kew Gard. Misc. 9: 17. 1857.— Cnemidostachys linearifolia Miq., Fl. Ind. Bat. Suppl. 1: 460. 1861.— Excoecaria chamaelea (L.) Baill., Adansonia 6: 323. 1867.— Sebastiania chamaelea (L.) Mόll.Arg. in DC., Prod. 15, 2: 1175. 1866; Airy Shaw, Kew Bull. 26: 339. 1972; Whitmore, Tree Fl. Mal. 2: 131. 1973.— Sebastiania chamaelea (L.) Mόll.Arg. var. asperococca (F.Muell.) Pax in Engl., Pflanzenr. IV.147.v: 117. 1912.


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Perennial herb to many-stemmed subshrub, up to 90 cm tall and 30 cm in diameter; taproot c. 15 cm long, yellowish-brown. Stipules 0.6–2 by 0.2–0.5 mm. Leaves: petiole 0.1–0.25 cm long; blade elliptic to lineal, 1.6–6 by 0.3–0.8(–1.2) cm, length/width ratio 5–6, base acute to obtuse, margin with appressed teeth, apex rounded to mucronate, lower surface glabrescent, with 0–6 marginal glands per side, secondary veins 13–35 pairs per side. Inflorescences: staminate part 5–15 by 1–1.5 mm. Bracts of staminate cymules c. 0.4 mm long, nearly completely covered by glands. Staminate flowers single, pedicel 0.2–0.4 mm long; sepals 0.5 mm long, ciliate. Pistillate flowers: sepals 0.6–1.2 mm long, ciliate; ovary glabrous; stigmata filiform, c. 0.5–1 by 0.1 mm. Fruits 3.5–4.5 mm long, green, turning pinkish to olive brown to orange, with 0.6–1 mm long excrescences in 6 rows of 5 or 6 each. Seeds 2.5–2.75 by 2–2.25 mm, brown, sometimes brown-yellowish-whitish mottled.

    T h a i l a n d.— EASTERN: Nakhon Ratchasima (Bua Yai, Hui Teleng, Pak Tong Chai, Sikhiu), Buri Ram, Ubon Ratchathani (Nong Khun); SOUTH-WESTERN: Ratchaburi (Bang Saphan, Huai Yang, Nong Kae), Prachuap Khiri Khan; SOUTH-EASTERN: Chanthaburi (Lake Liant); PENINSULAR: Surat Thani (Kantuli), Phuket (Airport, Patong Beach, Thalang), Satun (Ban Tahng Yahng), Songkhla (Klong Hoi Kong, Thung Lung), Pattani.

    D i s t r i b u t i o n.— Widespread in Africa (e.g., Cameroon, Togo) and in Asia from India and Sri Lanka to Vietnam and S China (type: Sri Lanka), the Solomon Islands and N Australia, absent in the Philippines and New Guinea.

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    E c o l o g y.— On beaches, sandy sites, roadsides and waste places, also on lateritic outcrops, grass fields and open woodland, often gregarious. Soil: sand, alluvial and lateritic ground. Altitude sea level up to 300 m. Flowers and fruits collected the whole year through, but particularly in the rainy season.

    V e r n a c u l a rSoi nok (สร้อยนก) (General).

    U s e s.— Whole young plants are cooked together with meat and vegetables for speedy recovery of women after giving birth [S (Mamit) 35141]. The plant is used as astringent tonic against diarrhoea and syphilis in India.

    N o t e.— Microstachys chamaelea is sometimes confused with Sauropus bacciformis (L.) Airy Shaw in the herbaria, a herb with similar habit but with entire leaves and smooth fruits with petals and carinate, reddish seeds.