Flora of Thailand

Euphorbiaceae

 

66. Omphalea

 

L.J. Gillespie

 

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Genus description

Identification key

Species description

 

Omphalea

 

L., Syst. Nat. ed. 10, 2: 1264. 1759; A.Juss., Euphorb. Gen.: 54. 1824; Baill., Ιtude Euphorb.: 527. 1858. Mόll.Arg. in DC., Prodr. 15, 2: 1134. 1866; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.v: 14. 1912; Airy Shaw, Kew Bull. 26: 310. 1972; Whitmore, Tree Fl. Mal. 2: 120. 1973; Airy Shaw, Kew Bull. Add. Ser. 4: 179. 1975; G.L.Webster, Ann. Missouri Bot. Gard. 81: 96. 1994; Radcl.-Sm., Gen. Euphorbiacearum: 264. 2001; Wurdack, Petra Hoffm. & M.W.Chase, Amer. J. Bot. 92: 1397. 2005; Gillespie in Welzen & Chayam., Fl. Thailand 8, 2: 457. 2007; G.L.Webster in Kubitzki, Fam. Gen. Vasc. Pl. 11: 159, Fig. 36. 2014.— Hecatea Thouars, Hist. Vιg. Ξles France 27, tab. 5. 1804.— Neomphalea Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.xiv: 54. 1919.

 

Trees, shrubs or lianas, monoecious; latex copious to scant, usually reddish; foliage evergreen or deciduous. Indumentum of simple hairs, plants pubescent to glabrescent.  Stipules small, triangular, caducous.  Leaves alternate, simple, petiolate, often ontogenetically heteromorphic (juvenile and adult leaves differ in size and shape); blades symmetric; papery to leathery, margin entire or rarely palmately lobed (outside of Asia), venation pinnate or palmate, with 2 glands on adaxial surface at blade base or petiole apex, and with laminar glands usually present on abaxial blade surface.  Inflorescences thyrses, appearing spicate, racemose, or paniculate, terminal, one to several produced sympodially at branch end; cymose units bisexual or distal ones staminate, lax to glomerate, each subtended by a bract, central flower(s) usually pistillate; bracts often large and leaf-like, usually stipulate and petiolate, biglandular or eglandular; bracteoles small, triangular, usually eglandular.  Flowers actinomorphic, pedicellate; petals absent.  Staminate flowers: sepals (4)5, imbricate; disc extrastaminal, annular or conical-annular, rarely 5-segmented, or scarcely developed; stamens 2 or 3; anthers free with connectives not or little expanded (Asia to Australia) or connate with connectives greatly expanded and fused into a massive hemi-spheroidal mushroom-shaped cap (Africa, neotropics); staminal column elongate, scarcely developed, or absent; pistillode absent.  Pistillate flowers: sepals (4)5; disc absent; ovary 3-locular, 1 ovule per locule, styles entirely connate into a massive column, sometimes very short or apparently absent, apex usually with 3 small stigmas surrounding a pore.  Fruits schizocarpous capsules or berries, 3-lobed to subglobose, pericarp woody or fleshy.  Seeds 3, subglobose, ellipsoid, or ovoid, ecarunculate.

    Pantropical genus of c. 20 species; one or two species in Thailand. Classification: subfam. Crotonoideae, tribe Adenoclineae, according to recent molecular evidence (Wurdack et al., 2005). The genus has long been considered of uncertain affinity within the uniovulate euphorbs, and has traditionally been treated in its own tribe Omphaleae, considered by Webster (1994) and Radcliffe-Smith ( 2001) as related to tribe Plukenetieae, subfam. Acalyphoideae.

 

Key to the species

 

1a.

Fruit capsular (woody, dehiscent), 3-lobed, 1.8—2.6 by 2.9—4.2 cm, smooth when dry. Seeds 1.7—2.1 cm long, mostly smooth, shiny, pale brown. Gynoecium oblong-obovoid to subglobose, apex broadly truncate. Inflorescence branch axes pubescent, drying pale green or pale brown. Juvenile leaves narrowly oblong-elliptic, to 8 cm wide

1. O. bracteata

1b.

Fruit fleshy, indehiscent, subglobose, 3.4—5.4 by 3.7—6 cm when dry, becoming deeply wrinkled. Seeds 2.5—3.6 cm long, rough, dull, medium brown. Gynoecium ovoid to subglobose, apex obtuse or rounded. Inflorescence branch axes very sparsely pubescent to glabrescent, often drying dark reddish or purplish brown. Juvenile leaves ovate, to 23 cm wide

2. O. sargentii

 

1. Omphalea bracteata (Blanco) Merr., Spec. Blancoan. 230. 1918; Enum. Philipp. Fl. Pl. 2: 457. 1923; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.xvii: 198. 1924; Chatterjee, Kew Bull. 3: 374. 1948; Airy Shaw, Kew Bull. 20: 414. 1965; Kew Bull. 26: 310. 1972; Whitmore, Tree Fl. Mal. 2: 120. 1973; Airy Shaw, Kew Bull. Add. Ser. 4: 180. 1975; Gillespie in Welzen & Chayam., Fl. Thailand 8, 2: 458, Fig. 48: A-H. 2007.— Tragia bracteata Blanco, Fl. Filip. ed. 2, 480. 1845.— Omphalea philippinensis Merrill, Philipp. J. Sci. 3: 236. 1908; Pax & K.Hoffm. in Engl., Pflanzenr. IV.147.v: 17. 1912.

 

           

 

Lianas up to 15 m in height; branches sparsely pubescent to glabrescent; tendril-like shoots 10—40 cm long, with strongly reflexed hook-like branches 0.5—2 cm long; foliage evergreen.  Leaves: petiole 1—4.5 cm long, glabrous; blades narrowly oblong-elliptic, 10—25 by 3—9 cm, length/width ratio (1.7—)2.4—5, somewhat leathery, glabrous, usually drying pale greyish green, base acute or sometimes obtuse, with two round glands adaxially, apex acuminate; venation pinnate with basal lateral pair of nerves usually weak or absent, nerves 6-11 per side; understory leaves with petioles to 12 cm long and blades to 40 by 11 cm, juvenile leaves with petioles to 7 cm long and blades narrowly oblong-elliptic, to 30 by 8 cm.  Inflorescences paniculate thyrses, 10—70 cm long, highly branched; axes sparsely to moderately pubescent, often becoming glabrescent, minor axes pale green or pale brownish when dry; main branches 4—14, to 30 cm long; main axis persistent, often tendrillate, with strongly recurved, hook-like branch bases; cymose units very condensed with flowers appearing fasciculate; bracts to 8 by 1.6(—2.6) cm, petiolate, biglandular, blade obovate or narrowly elliptic, apex acute. Staminate flowers: pedicel 6—14 mm long; sepals (4)5, 1.3—2.3 mm long and wide, apex obtuse or rounded, very sparsely pubescent; disc subannular, indistinct; androecium of 3 free, subsessile anthers fused basally.  Pistillate flowers: pedicel 3—12 mm long; sepals 5, broadly to very broadly ovate, 1—1.8 mm long and wide, very sparsely to sparsely pubescent; gynoecium broadly oblong-obovoid, becoming subglobose post anthesis, 1.6—3 by 1.4—2.8 mm, apex broadly truncate and depressed, glabrous; stylar column present as broadly truncate apex, 0.3—0.5 by 0.9—1.5 mm.  Fruits schizocarpous capsules, 3-lobed, 1.8—2.6 by 2.9—4.2 cm, separating into 3 loculicidally dehiscent cocci; pericarp 1.5—2 mm thick, smooth, becoming hard (woody) and brittle. Seeds subglobose or broadly ellipsoid, 1.5—2.9 by 1.4—2.5 by 1.2—2.1 cm, pale brown, semi-glossy, mostly smooth; outer seed coat very thin, adherent, persistent.

    T h a i l a n d.— NORTH-EASTERN: Nong Khai. SOUTH-WESTERN: Phetchaburi. SOUTH-EASTERN: Chanthaburi. PENINSULAR: Narathiwat (Sa Long), only one confirmed collection; a second collection from the same area (Nikom Waeng) is likely to be this species, but may be the following species.

    D i s t r i b u t i o n.— Burma?, Laos?, Malay Peninsula, Borneo (Brunei, Sabah, Kalimantan), and the Philippines (type); common in parts of Borneo and the Philippines, but rare in Southeast Asia. 

    E c o l o g yGenerally found in lowland evergreen primary forest, often Dipterocarp forest, sometimes secondary forest, on level land, hill sides, riverbanks, and coastal areas; soils: recorded on red and ultrabasic soils.  Altitude: sea-level to 650 m.

    N o t e sOmphalea bracteata and O. sargentii are difficult to distinguish without fruit. This is particularly the case in Southeast Asia, where few collections are known and leaf and floral characters show a different pattern of variation compared to Malesian collections. Both species are common in Borneo, and rare to uncommon in the Malay Peninsula. Collections from Burma and Laos have not yet been verified as to species, but have previously been identified as O. bracteata; these either lack fruit or have not been examined here.

 

2. Omphalea sargentii Merr., Philipp. J. Sci. 11: 574. 1920; Enum. Philipp. Fl. Pl. 2: 457. 1923; Philipp. J. Sci. 29: 386. 1926; Gillespie in Welzen & Chayam., Fl. Thailand 8, 2: 460, Fig. 48: I-K. 2007.

 

   

 

Lianas up to 23 m in height, to ca. 22 cm in diameter; branches glabrous or glabrescent; tendril-like shoots with short hook-like branches; foliage evergreen.  Leaves: petioles 1—4(—8) cm long, glabrous or sometimes very sparsely pubescent; blades ovate, elliptic or rarely obovate, 13—29 by 5—14 cm, length/width ratio 1.5—3, somewhat leathery, glabrous, usually drying brownish, base obtuse, rounded, or rarely acute, with two round glands adaxially, apex acuminate; venation pinnate with basal lateral pair of nerves often prominent and diverging at a steep angle, nerves 6-11 per side; understory and juvenile leaves with petioles to 21 cm and blades to 40 by 23 cm. Inflorescences paniculate thyrses, 20—70 cm long, highly branched; axes glabrous or very sparsely pubescent, minor axes dark reddish brown or purplish when dry; main branches 2—20, to 50 cm long, main axis persistent, often becoming tendrillate, with strongly recurved, hook-like branch bases; cymose units very condensed with flowers appearing fasciculate; bracts to 12 by 3 cm, petiolate, biglandular; blade obovate or narrowly elliptic, apex obtuse or acute.  Staminate flowers: pedicel 6—16 mm long; sepals 5, 1—2 mm long and wide, apex rounded or broadly obtuse, glabrous to very sparsely pubescent; disc subannular, indistinct; androecium of 3 free, subsessile anthers fused basally.  Pistillate flowers: pedicel 4—14 mm long; sepals 5, suborbicular to broadly ovate, 1—2.5 mm long and wide, glabrous to very sparsely pubescent; gynoecium ovoid or subglobose, 1.7—3.2 by 1.5—2.8 mm, apex obtuse or rounded, glabrous; stylar column absent or present as small conical apex, to 0.5 by 1.2 mm.  Fruits indehiscent, subglobose, 3.4—5.4 by 3.7—6 cm when dry; pericarp fleshy, 3—6 mm thick and deeply wrinkled when dry. Seeds broadly ellipsoid, radially compressed, 2.5—3.6 by 2.3—3.3 by 1.7—2.2 cm, medium brown, dull, rough, minutely verrucate; outer seed coat thin, whitish, papery when dry, not persistent.

    T h a i l a n d.— No confirmed collections, but may be expected in Peninsular Thailand. 

    D i s t r i b u t i o n.— Malay Peninsula, Borneo (Sabah, Kalimantan), Sulawesi, and the Philippines (type; only known from Bancalan, S of Palawan). 

    E c o l o g yLowland evergreen primary forest, sometimes in secondary forest, on level land, low hills or near rivers; soils: clay, poor sandy, gravel terrace. Altitude: sea-level to 350 m.

    N o t e. — See notes under former species.