Flora of Thailand Euphorbiaceae

 

74. Ptychopyxis

 

P.C. van Welzen & K. Chayamarit

 

Goto on this page:

Genus description

Identification key

Species description

Miq., Fl. Ned. Ind. Suppl. 402. 1861; Hook.f., Fl. Br. Ind. 5: 454. 1887; Hook. Icon. Pl. 18: t.1703. 1887; Croizat, J. Arnold Arbor. 23: 47. 1942; Airy Shaw, Kew Bull. 14: 363. 1960; 16: 347. 1963; Whitmore, Tree Fl. Mal. 2: 126. 1973; Airy Shaw, Kew Bull. Add. Ser. 4: 188. 1975; Kew Bull. Add. Ser. 8: 197. 1980; Kew Bull. 36: 340. 1981; G.L.Webster, Ann. Missouri Bot. Gard. 81: 77. 1994; Radcl.-Sm., Gen. Euphorbiacearum: 172, fig. 20. 2001; Welzen & Chayam. in Welzen & Chayam., Fl. Thailand 8, 2: 512. 2007; Stoops & Welzen, Nordic J. Bot. 31: 95. 2013; G.L.Webster in Kubitzki, Fam. Gen. Vasc. Pl. 11: 125. 2014. — Clarorivinia Pax & Hoffm. in Engl., Pflanzenr. IV.147.vii: 17. 1914.

Trees, usually small, dioecious, twigs stout, velvety. Indumentum simple hairs, usualy ferrugineous. Stipules minute, margin entire. Leaves alternate, simple, rather crowded at the top of the twigs; petiole strongly kneed at both ends, often velvety; blade coriaceous, usually without glands and domatia; venation penninerved, scalariform. Inflorescences axillary to terminal, racemes to panicles; staminate ones with groups of flowers per node, pistillate ones with single flowers per node; bracts small. Flowers usually pedicelled, calyx valvate, petals absent. Staminate flowers pedicelled; sepals 3-5, unequal, thick; disc glands numerous, small, hairy enations, among stamens; stamens 35-65, in a dense globose head on a convex receptacle, filaments free, anthers with 4 thecae, 2 upper larger than 2 lower; pistillode absent. Pistillate flowers subsessile to shortly pedicelled; sepals 4 or 5, elliptic, thick, unequal; disc narrow, annular; ovary 2—4-locular, one ovule per locule, style short, stigmas recurved, apically not split. Fruits subglobose capsules, tardily splitting, densely furry outside, usually variously ridged. Seeds oblong, ecarunculate.

    A tropical Asian genus of 10-12 species distributed from Thailand through Indonesia to the Philippines and New Guinea. Possibly two species in Thailand.

1.  Ptychopyxis javanica (J.J.Sm.) Croizat, J. Arnold Arbor. 23: 49. 1942; Airy Shaw, Kew Bull. 14: 371. 1960; Backer & Bakh.f., Fl. Java.: 479. 1963; Airy Shaw, Kew Bull. 26: 327. 1972; Welzen & Chayam. in Welzen & Chayam., Fl. Thailand 8, 2: 512, Fig. 67C-G. 2007; Stoops & Welzen, Nordic J. Bot. 31: 107, Fig. 11c–g, 12. 2013.— Podadenia javanica J.J. Sm., Meded. Dept. Landb. Ned.-Indië 10: 388. 1910.— Ptychopyxis angustifolia Gage, Rec. Bot. Surv. Ind. 9: 248. 1922.

Small trees to trees, up to 30 m high, up to 45 cm in diameter; bole straight with basally small buttresses. Outer bark pale brown and green to grey, flaking in small brittle pieces; inner bark pale whitish to light yellow to brown; sapwood white to yellowish, with thin rays. Stipules not seen. Leaves: petiole 1.9—4.3 cm long, especially apically pulvinate, round, subglabrous to hairy; blade elliptic to oblong, 11.3—24.5 by 3.7—7.8 cm, length/width ratio 3.1—5, chartaceous to coriaceous, base cuneate, margin entire, apex acuminate, sometimes round extrafloral nectaries on both surfaces, mainly in lower half of blade, lower surface often slightly hairy, venation distinct on both sides, nerves 8—15 pairs, veins scalariform. Inflorescences axillary racemes or narrow panicles, up to 10.5 cm long, golden brownish tomentose; bracts triangular, 1.5—2 by 0.6—1 mm. Flowers greenish to yellow. Staminate flowers only known in bud; upper part pedicel c. 2.7 mm long, tomentose; sepals hairy, especially outside. Pistillate flowers subsessile to pedicel up to 3 mm; sepals 5 or 6, triangular to ovate, c. 2 b y1—1.3 mm, hairy; disc densly hairy; ovary (2)3(4)-locular, stigmas c. 1.5 mm long. Fruits globose or pyriform, dorsoventrally flattened and symmetric, 1.7—3 by 1.6—2.2 by 1.4.—1.6 cm, brown tomentellous. Seeds ovoid, dorsoventrally compressed, c. 13 by 8 by 6 mm.

    T h a i l a n d.— PENINSULAR: Phatthalung (Klong Huai Khao), Nakhon Si Thammarat (Khao Luang).

    D i s t r i b u t i o n.— Malay Peninsula,

    Ecology.— In evergreen forest and secondary forest; soil sandy. Altitude: 180—800 m.

    Vernacular.— Plao thuean (เปล้าเถื่อน) (Peninsular).

2.  Ptychopyxis plagiocarpa Airy Shaw, Kew Bull. 14: 372. 1960; Kew Bull. 26: 327. 1971; Welzen & Chayam. in Welzen & Chayam., Fl. Thailand 8, 2: 513, Fig. 67A-B. 2007.

Tree up to 30 m high, up to 50 cm in diameter; bole up to 15 m high. Outer bark thin, smooth, grey; inner bark tan coloured; sapwood white, heartwood pale brown. Stipules not seen. Leaves: petiole 1—2 cm long, pulvinate at both ends; blade elliptic to oblong, 9.5—16 by 3—5.5 cm, length/width ratio 3—3.1, chartaceous to coriaceous, base obtuse to cuneate, margin flat, apex acuminate, glabrous, upper surface shiny when fresh, venation mainly prominent beneath, nerves 8—10, veins scalariform. Staminate inflorescences, staminate flowers, and pistillate flowers unknown. Infructescences up to 8.5 cm long, hairy, bracts triangular, 1.5—2.3 by c. 1 mm, hairy. Fruit ellipsoid-oblong, dorsoventrally flattened, 16—25 by 11-18 by 11—14 mm, mainly dorsoventrally asymmetric, sulcate apically and especially basally (seldom symmetric), golden or dark brownish tomentose, 2- (or 3)-locular; pedicels c. 2.5 mm, with subapical abscission zone, thickened above this zone; sepals persistent, 5 or 6, triangular, c. 1.5 by 1 mm, hairy; wall woody. Seeds ellipsoid, dorsoventrally flattened, 11—17 by 10—11 by c. 7 mm.

    T h a i l a n d.— SOUTH-WESTERN: Kanchanaburi (near Wang Ka).

    D i s t r i b u t i o n.— Endemic in Thailand (type: Kanchanaburi, near Neeckey (near Wangka), near Ran Ti River, KASIN (Kwae Noi Basin Expedition) 173, holo in K, iso in L).

    E c o l o g y.— Alluvial, partly open areas in mixed evergreen and deciduous hardwood forest, seasonally flooded; limestone. Altitude: 150—200 m.

    N o t e.— The differences between this species and P. javanica are not very clear. The only real difference is the asymmetry of the fruit. Tthere is overlap in the number of locules of the ovary (P. javanica may also have 2-locular fruits) and in the colour of the hairs (a second collection of P. plagiocarpa from Kanchanaburi, Maxwell 94-535, has the typical asymmetric fruits, but the hairs are dark brown and not golden; while a specimen from Southern Thailand, van Beusekom & Phengklai 853, with symmetric ovaries like P. javanica has golden hairs). It is still far from clear whether there are indeed two species or that the Kanchanaburi specimens constitute a local mutation of P. javanica. Unfortunately, no staminate specimens of P. plagiocarpa are known, and only budding ones of P. javanica.