Flora of Thailand
P.C. van Welzen
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Pierre ex Gagnep., Bull. Soc. Bot. France 71: 878. 1924; in Lecomte, Fl. Indo-Chine 5: 299. 1925; Pax & K.Hoffm. in Engl. & Harms, Natόrl. Pflanzenfam. ed. 2, 19c: 90. 1931; Airy Shaw, Kew Bull. 19: 308. 1965; Kew Bull. 26: 343. 1972; G.L.Webster, Ann. Missouri Bot. Gard. 81: 75. 1994; Welzen, Blumea 44: 431. 1999; Radcl.-Sm., Gen. Euphorbiacearum: 148. 2001; Welzen in Welzen & Chayam., Fl. Thailand 8, 2: 566. 2007; G.L.Webster in Kubitzki, Fam. Gen. Vasc. Pl. 11: 142. 2014.
Herb-like shrubs to trees, monoecious. Indumentum consisting of very dense, sessile and peduncled stellate hairs. Stipules caducous. Leaves spirally arranged, simple; blade ovately orbicular to ovate, coriaceous, symmetric, base emarginate (to truncate), with a rim along the point of attachment with the petiole, margin entire to shallowly crenate, apex rounded (to acute and mucronulate), lower surface with subsessile glands; venation palmate with at least 5 distinct basal nerves, secondary nerves looped and joined near margin, veins scalariform. Inflorescences terminal racemes, single, basal flowers pistillate, apical ones staminate. Flowers actinomorphic, single per bract; sepals 5, valvate; disc glabrous. Staminate flowers subsessile to pedicellate; sepals ovately elliptic; petals 5 (or 6), obovate, shorter to slightly longer than sepals; disc annular or separate lobes; stamens 40-60, filaments united into a column, anthers basifixed, 2-locular; pistillode absent. Pistillate flowers sessile to subsessile; sepals linear; petals absent; disc annular; pistil 3-locular, one ovule per locule, smooth, tomentose. Fruits slightly lobed capsules, triangular in transverse section, outside densely tomentose, inside glabrous. Seeds covered by a thin, translucent sarcotesta.
Monotypic genus, distribution as the species. Classification: Subfam. Acalyphoideae, tribe Chrozophoreae, subtribe Doryxylinae.
Thyrsanthera suborbicularis Pierre ex Gagnep., Bull. Soc. Bot. France 71: 878. 1924; in Lecomte, Fl. Indo-Chine 5: 299, fig. 32: 2-6; fig. 33: 1, 2, 2. 1925; Airy Shaw, Kew Bull. 19: 308. 1965; Kew Bull. 26: 343. 1972; Welzen, Blumea 44: 432, fig. 5, map 4. 1999; in Welzen & Chayam., Fl. Thailand 8, 2: 568, Fig. 89. 2007.
Herb-like shrubs to trees, 20 cm up to 2(-20?) m high. Stipules c. 2.3 by 0.4 mm. Leaves: petiole 2.8-6 cm long; blade 3.8-17 by 3.2-15 cm, length/width index 0.9-1.3, glabrous above when old, tomentose underneath, nerves 3-5 per side of the midrib. Inflorescences up to 6(-16) cm long. Staminate flowers 4.5-9 mm in diameter, light yellow; pedicel 2.2-4.5 mm long; sepals 4-4.5 by 1.2-1.6 mm, apex hooked inwards; petals 3.2-5.5 by 1.2-2.1 mm, androphore 3.3-3.5 mm long, lower 1.5-3 mm without filaments; anthers 0.3-0.5 by 0.3-0.5 mm, yellow. Pistillate flowers 5-7 mm in diameter; pedicel 0-2 mm long; sepals 3.3-6.3 by c. 0.2 mm; ovary ovoid, 5-7 by 3-5.5 mm wide. Fruits c. 10 by 7 mm. Seeds 4.2-4.5 by 3.8-4 mm in diameter
T h a i l a n d. NORTHERN: Kamphaeng Phet; EASTERN: Chaiyaphum (Nong Bua Deng), Buri Ram; CENTRAL: Lop Buri (Lam Narai), Saraburi (Sam Lan); SOUTH-EASTERN: Prachin Buri (Aranyaprathet, Watana). Nakhon Sawan (Hua Wai)
D i s t r i b u t i o n. Thailand, Kampuchea (type), and Vietnam.
E c o l o g y. Roadside, waste land, open, rocky-sandy areas, thickets, secondary bushes. Altitude: 50-100 m. Flowering and fruiting throughout the year, but mainly around August. Probably fire-resistant (short plant above ground, more elaborate and thicker root system underground; see also Airy Shaw, 1965), and coloniser of waste ground.
V e r n a c u l a r. Po kapla (ปอกะปลา) (Nakhon Sawan).
U s e s. Well-known in Indochina, used as injection or during washing by women giving birth (Gagnepain 1925).
N o t e. A somewhat variable species, in Vietnam the glands on the lower leaf surface are much larger and situated in a submarginal row, while elsewhere the glands are much smaller and scattered all over the leaf. In Thailand one specimen had distinctly pedicelled staminate and pistillate flowers (Maxwell 75-115), while all other specimens mainly have subsessile staminate and sessile pistillate flowers.