Flora of Thailand
Euphorbiaceae
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L., Sp. Pl.: 1035. 1753; Müll.Arg. in DC., Prod. 15, 2: 794. 1866; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.vii: 271. 1914; G.L.Webster, J. Arnold Arbor. 48: 366. 1927; Tutin, Fl. Europaea 2: 212. 1968; G.L.Webster, Ann. Missouri Bot. Gard. 81. 85. 1994; Radcl.-Sm., Gen. Euphorbiacearum: 205. 2001; Welzen in in Welzen & Chayam., Fl. Thailand 8, 2: 446. 2007; G.L.Webster in Kubitzki, Fam. Gen. Vasc. Pl. 11: 122. 2014.
Herbs, monoecious. Indumentum of simple, echinate trichomes. Stipules late caducous, basally and apical glandular. Leaves opposite, distichous, simple; petiole with apically 1–3 glands at each side; blade symmetric, papery, basally attached, margin serrate with glandular teeth; venation pinnate, nerves looped and joined near margin, veins and veinlets reticulate. Inflorescences axillary spikes, single, with flowers in small groups per node, either completely staminate, or in upper nodes also pistillate flowers (then staminate ones not flowering). Flowers actinomorphic, (subs)sessile; sepals 3, valvate, ovate; petals and disc absent. Staminate flowers: stamens 12 or 13, free; anthers 2-locular, completely separated from each other by a minute connective; pistillode absent. Pistillate flowers: staminodes 2, filament-like; ovary 2-locular, one ovule per locule; style almost absent; stigmas short, not lobed. Fruits capsules, lobed. Seed globose, verrucose, without arilloid.
Eight species, seven in Europe and Mediterranean Africa, one in east temperate Asia touching N. Thailand. Classification: Subfam.: Acalyphoideae, tribe Acalypheae, subtribe Mercurialinae.
Mercurialis leiocarpa Sieb. & Zucc., Abh. Bayer. Akad. Math.-Naturwiss. Kl. 4: 145. 1845; Müll.Arg. in DC., Prod. 15, 2: 795. 1866; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.vii: 280. 1914; Airy Shaw, Kew Bull. 26: 310. 1972; Welzen in Welzen & Chayam., Fl. Thailand 8, 2: 447, Fig. 43. 2007.
Herbs up to 1 m high. Stipules 2–2.8 by c. 1.2 mm. Leaves: petiole 1.3–5.5 cm long; blade ovate, 5.5–13.5 by 2.3–5.2 cm, index 2.3–3, glossy dark green above, base obtuse to attenuate, apex (acuminate to) cuspidate, echinate hairs sparse on both sides of veins; nerves 11 or 12 per side. Inflorescences up to 12 cm long. Flowers green (to white). Staminate flowers 3.5–3.8 mm in diameter; sepals 1.7–2.1 by 1–1.6 mm; stamens: filaments 1.7–2 mm long, anthers c. 0.6 by 0.3 mm, yellow. Pistillate flowers 2–3 mm in diameter; sepals 1.3–1.7 by 0.9–1.2 mm; staminodes 2.2–2.4 mm long; ovary 0.8–1.2 by 0.6–0.8 mm; style 0.2–0.3 mm long; stigmas 0.7–1.1 mm long. Fruits 5.3–6.5 by 3–3.8 mm, glabrous, somewhat setulose, green. Seeds c. 2.4 in diam.
T h a i l a n d.— NORTHERN: Chiang Mai (Doi Angka, Doi Inthanon).
D i s t r i b u t i o n.— E. Himalaya, N. Assam, N. Thailand, S.W. and C. China, Taiwan, and Japan (type).
E c o l o g y.— Hill evergreen forest, evergreen forest, mossy forest; locally many in moist to marshy places, also on open ridges; bedrock granite; altitude: 1750–2690 m.
N o t e.— According to Airy Shaw (1972) only slightly different from the European M. perennis L., from which it mainly differs in its glabrous ovary and fruit (though the latter may be somewhat setulose).