Flora of Thailand

Euphorbiaceae

 

38. Euphorbia

 

H.-J. Esser

 

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Genus description

Identification key

Species descriptions

Cultivated species

 

Euphorbia

 

L., Sp. Pl.: 450. 1753; Boiss. in DC., Prodr. 15, 2: 7. 1862; Benth., Gen. Pl. 3: 258. 1880; Pax & K.Hoffm., Natürl. Pflanzenfam. ed. 2, 19c: 208. 1931; Radcl.-Sm., Kew Bull. 26: 261. 1972; G.L.Webster, Ann. Missouri Bot. Gard. 81: 128. 1994; Radcl.-Sm., Gen. Euphorbiacearum: 405. 2001; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 263. 2005; G.L.Webster in Kubitzki, Fam. Gen. Vasc. Pl. 11: 207. 2014.— Chamaesyce S.F.Gray, Nat. Arr. Brit. Pl.: 2: 260. 1821; Wheeler, Rhodora 43: 97. 1941; G.L.Webster, Ann. Missouri Bot. Gard. 81: 129. 1994.— Euphorbia L. sect. Chamaesyce (S.F.Gray) Rchb., Fl. Germ. Excurs.: 755. 1832.— Euphorbia L. subgen. Chamaesyce (S.F.Gray) Caes. ex Rchb., Rep. Herb. Nom. Gen. Pl.: 193. 1841.— Poinsettia Graham, Edinb. New Philos. J. 20: 412. 1836.— Euphorbia L. subgen. Poinsettia (Graham) House, Bull. New York State Mus. 254: 472. 1924.

 

Herbs or shrub, monoecious, succulent or not, spiny or not; branching alternate or dichotomous, or main axis aborting above the cotyledons and continued by sympodial growth, or unbranched; latex white. Indumentum absent or consisting of multicellular, unbranched hairs. Stipules absent, transformed into spines, interpetiolar and variously fused, or simple to divided. Leaves alternate, opposite, in the floral region sometimes verticillate, persistent or caducous; petiole distinct to absent, eglandular; blade simple, symmetric or oblique, variable in shape and margin, eglandular. Inflorescences as cyathia, pseudanthial, radially symmetric, usually bisexual, the fused bracts forming a cupular involucrum, with 1-5 glands and often variously shaped petaloid appendages, and 5 alternating erect lobes; cyathia solitary or grouped in dichotomous or umbellate terminal or axillary cymes, their bracts variously coloured and often showy. Individual flowers with much reduced to absent sepals, without petals or disc; bracteoles ciliate to fimbriate. Staminate flowers lateral, in condensed monochasia, reduced to a single stamen; stamen with anthers 2-locular, basifixed. Pistillate flowers terminal, usually pedicellate, consisting only of the reduced to absent calyx and the ovary; ovary 2-or 3-locular, smooth, with 1 ovule per carpel; style column present or absent, stigmas apically bifid. Fruits 2-or 3-locular, small to large, globose to deeply sulcate, smooth, pubescent to glabrous, dry and dehiscent. Seeds 2 or 3 per fruit, ovoid-ellipsoid, glabrous, with smooth or variously sculptured surface, sometimes with a hyaline-whitish coating, dry, with or without caruncle.

    One of the largest genera of flowering plants with c. 2000 species (depending on the delimitation), most of them in arid or temperate to subtropical regions. 21 naturally occuring species in Thailand, most of them introduced, and at least 7 cultivated ones. Classification: subfam. Euphorbioideae, tribe Euphorbieae, subtribe Euphorbiinae.

    N o t e s.— In this revision, a broad concept of Euphorbia is applied, including Chamaesyce and Poinsettia (but excluding Pedilanthus), in agreement with the limits applied by Radcliffe Smith in Airy Shaw (1972). This is basically supported by recent molecular studies (except that also Pedilanthus probably should be united). The Thai species are divided over 8 sections (or subgenera): Alectoroctonum (non-succulent shrubs with leaves in whorls or opposite, cyathial glands 4-5, with appendages), Caulanthium or Goniostema (poorly understood; unbranched geophytes, succulent, not spiny, leaves alternate, cyathia axillary, their glands 4-5 glands, without appendages), Chamaesyce (herbs with sympodial growth, opposite leaves and large interpetiolar stipules, cyathial glands 4-5, with appendages), Euphorbia (succulents with deciduous leaves, spines in pairs on spine-shields, cyathial glands 4, without appendages), Esula (herbs with alternate leaves, flowering branches in whorls, cyathial glands 4-5, falcate to bicornute, without appendages), Lacanthis (succulent shrubs, spines present, not on spine-shields, leaves always present, cyathial bracts brightly coloured, glands 4, without appendages), Poinsettia (herbs or shrubs with alternate leaves, cyathial glands 1, without appendage), and Tirucalli (succulent shrubs without spines, leaves deciduous, glands 4, without appendages).

    Euphorbia is a widely cultivated genus, and certainly more species can be found in occasional cultivation. Only species verified with collections or cultivars for this study have been included here. Euphorbia tortilis Rottler (som chao yai), formerly mentioned for Thailand, was not verified; this name was misapplied quite often, mostly for E. antiquorum or E. lactea.

 

Key to the indigenous and cultivated species

(cultivated species treated separately at the end)

 

1a.

Plants succulent, spiny, cactus-like.

2

1b.

Plants herbaceous to woody, slightly succulent or not, not spiny.

8

2a.

Spines solitary or in groups, not on spine-shields. Cyathial bracts conspicuous, with bright colours.

25. E. milii

2b.

Spines in pairs on spine-shields. Cyathial bracts inconspicuous, not in bright colours.

3

3a.

Spines in (4-)5 rows.

4

3b.

Spines in 3(-4) rows.

5

4a.

Branches nearly round with slight angles only. Leaves persistent for a longer time, large (10-18 cm long).

26. E. neriifolia

4b.

Branches with distinct angles and wings. Leaves unknown, caducous, probably smaller .

21. E. sp.

5a.

Branches drying greyish-green. Spine-shields (1.5-)2.5-4.5 cm apart, the sinuses between them usually more than 5 mm deep. Spines greyish-to yellowish-brown, deciduous. Fruits 12-15 mm in diam.

9. E. lacei

5b.

Branches drying green (rarely plants whitish). Spine-shields 1-2 cm apart, the sinuses between them shallow, up to 5 mm deep. Spines dark brown to blackish, persistent. Fruits up to 7 mm in diam., or plants always sterile.

6

6a.

Plants in natural environments, flowering and fruiting. Leaves very soon deciduous, not known from Thai plants.

1. E. antiquorum

6b.

Plants only known in cultivation, always sterile. Leaves deciduous, but often present.

7

7a.

Branches ascending but not parallel to and close to the main stem. Leaves scale-like, c. 4 mm long.

23. E. lactea

7b.

Branches ascending, parallel to and close to the main stem. Leaves obovate-elliptic, 10-30 mm long.

28. E. trigona

8a.

At least lower leaves alternate, or leaves absent.

9

8b.

Leaves present, all leaves opposite or whorled.

16

9a.

Dichotomously branched, succulent shrub with round branches, usually leafless.

27. E. tirucalli

9b.

Plants with distinct leaves (if leafless and succulent, then unbranched).

10

10a.

Unbranched plants with slightly succulent leaves and stems, leaves deciduous. Flowering plants leafless or with leaves. Cyathia axillary, solitary or per 3.

11

10b.

Non-succulent plants with persistent leaves, usually branched. Flowering plants with leaves. Cyathia in terminal inflorescences.

12

11a.

Plants without woody rootstock. Leaves distinctly (10-15 mm) petiolate. Cyathia in terminal leaf axils.

16. E. ridleyi

11b.

Plants with woody rootstock. Leaves subsessile. Cyathia in lower part of stem. 

19. E. sessiliflora

12a.

Leaves linear, up to 9 mm wide. Cyathial glands 4-5 glands, falcate to bicornute.

13

12b.

Leaves variously shaped, up to 9 cm wide, rarely linear. Cyathial glands 1, not falcate or bicornute.

14

13a.

Perennials with a woody rootstock. Fruits 3-locular.

12. E. prolifera

13b.

Annuals without a woody rootstock. Fruits 2-locular.

17. E. saxicola

14a.

Shrubs to 3 m tall. Cyathial bracts leaf-like, often deep red throughout. Leaves green. Cyathia 4-5 mm in diameter.

14. E. pulcherrima

14b.

Herbs to 1.5 m tall. Cyathial bracts inconspicuous, green. Uppermost leaves green to reddish or white, not deep red throughout. Cyathia less than 2 mm in diameter.

15

15a.

Uppermost leaves usually white or red at base only, often panduriform. Cyathia and fruits glabrous. Bract glands with a narrow-linear opening. Seeds ellipsoid, the apex not truncate.

6. E. cyathophora

15b.

Uppermost leaves green or whitish, but never reddish at base only, linear to elliptic, very rarely panduriform. Cyathia and fruits glabrous or pubescent. Bract glands with a circular opening. Seeds orbicular-ellipsoid, the apex truncate.

7. E. heterophylla

16a.

Leaves in whorls of 3, with a petiole nearly as long as the blade, usually pink to purplish-red throughout.

22. E. cotinifolia subsp. cotinoides

16b.

Leaves opposite, with a petiole much shorter than the blade, green or slightly reddish.

17

17a.

Shrubs up to 2 m tall. Petiole of leaves 7-20 mm long. Cyathial bracts distinct, white, petal-like.

24. E. leucocephala

17b.

Herbs or subshrubs up to 60 cm tall. Petiole of leaves up to 3 mm long. Cyathial bracts leaf-like or scaly, indistinct, green.

18

18a.

Plants glabrous.

19

18b.

Plants pubescent at least on some parts.

23

19a.

Fragile, loosely prostrate herb, often rooting at the nodes. Stipules whitish. Leaves very small, 2.5-4 by 2-3 mm.

18. E. serpens

19b.

Usually erect herb or shrub, not rooting at the nodes. Stipules green. Leaves larger than 4 by 3 mm.

20

20a.

Annual herb with hairlike branches, without woody rootstock. Leaves (elliptic-)obovate, very thin, the apical ones distinctly smaller. Cyathia solitary in leaf axil, subtended by leaf-like bracts. Appendages of cyathial glands undulate to fimbriate.

4. E. capillaris

20b.

Perennial, robust herb or with a distinctly woody base (subshrub). Leaves linear to elliptic (rarely obovate), moderately thick to succulent, the apical ones hardly smaller. Cyathia in condensed dichasial clusters, subtended by linear or scale-like bracts. Appendages of cyathial glands entire or absent.

21

21a.

Stems distinctly articulate. Leaves succulent, their venation hardly visible. Cyathial glands without appendages. Seeds smooth to slightly rugulose.

2. E. atoto

21b.

Stems not to slightly articulate. Leaves not succulent, their venation visible.Cyathial glands with large, entire, petal-like appendages. Seeds distinctly rugulose to foveolate.

22

22a.

Leaves linear to narrowly oblong-elliptic. Numerous (more than 3) cyathia in elongate, pedunculate dichasia.

3. E. bifida

22b.

Leaves (obovate-)elliptic. Few (c. 3) cyathia in subsessile dichasia.

10. E. parkeri

23a.

Plants with yellowish indumentum. Cyathia in axillary, pedunculate, capitate clusters of 20-50.

8. E. hirta

23b.

Plants with pale-hyalin, never yellowish indumentum. Cyathia in elongate dichasia or in small, terminal or subsessile clusters of less than 10 cyathia.

24

24a.

Subshrubs, usually with a woody rootstock. Leaves linear to oblong-elliptic. Appendages of cyathial glands 1-1.5 mm long, entire, petal-like.

3. E. bifida

24b.

Herbs or subshrubs without a woody rootstock. Leaves orbiculate to obovate or elliptic. Appendages of cyathial glands absent, shorter than 1 mm, or fimbriate-ciliate.

25

25a.

Hairs on fruits only in rows along the keels; often but not always hairs on stems in rows only.

13. E. prostrata

25b.

Fruits glabrous or pubescent throughout, hairs not on keels only; stems glabrous or pubescent without distinct rows.

26

26a.

Leaves in dense apical clusters, hiding the cyathia. Appendages of cyathial glands 1-2.5 mm long, fimbriate-ciliate, partly pubescent.

5. E. cristata

26b.

Leaves regularly spaced, not hiding the cyathia. Appendages of cyathial glands less than 1 mm long.

27

27a.

Hairs dense, curled to appressed, in particular on fruits. Fruits subsessile (pedicel shorter than the involucre), maturing within the oblique cyathium and surrounded by cyathial glands.

20. E. thymifolia

27b.

Hairs dense to scattered, erect in particular on fruits. Fruiting pedicel longer the involucre, fruits maturing outside of the symmetrical cyathium, not surrounded by cyathial glands.

28

28a.

Plants with scattered hairs. Cyathia solitary in leaf axil, subtended by a pair of leaf-like bracts. Appendages of cyathial glands fimbriate.

4. E. capillaris

28b.

Plants with scattered to dense hairs. Cyathia in axillary dichasia, subtended by pairs of linear; or scale-like bracts. Appendages of cyathial glands entire.

29

29a.

Leaves densely pubescent to subglabrous, obovate-ovate-elliptic (index usually more than 2).

11. E. parviflora

29b.

Leaves densely pubescent on both surfaces, broadly elliptic (index less than 2). Fruits densely tomentose.

15. E. reniformis

 

1. Euphorbia antiquorum L., Sp. Pl.: 450. 1753; ?Lour., Fl. Cochinch.: 298. 1790; ?Roxb., Fl. Ind. ed. 1832, 3: 468. 1832; ?Miq., Fl. Ind. Bat. 1, 2: 418. 1859; Boiss. in DC., Prodr. 15, 2: 81. 1862; Kurz, Forest Fl. Burma 2: 416. 1877; Hook.f., Fl. Br. India 5: 255. 1887; Ridl., Fl. Malay Penins. 3: 180. 1924; Gagnep. in Lecomte, Fl. Indo-Chine 5: 240, pl. 26 fig. 1-7. 1925; Burkill, Dict. Econ. Prod. Malay Pen. 1: 978. 1935; Croizat, Euphorb. Antiq.: 6. 1934; Backer & Bakh.f., Fl. Java 1: 501. 1964; Radcl.-Sm., Kew Bull. 26: 262. 1972; Whitmore, Tree Fl. Malaya 2: 96. 1973; C.S.Chun, Limestone Fl. Malaya: 236. 1973; Wijnands, Bot. Commelins: 96, plate. 1983; Corner, Wayside Trees Mal. ed. 3, 1: 290, fig. 84. 1988; P.H. Hô, Câyco Viêtnam 2, 1: 358, fig. 4662. 1992; J.S. Ma, Fl. Reipubl. Pop. Sin. 44(3): 62, pl. 15 fig. 4-7. 1997; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 266, fig. 67, plate XV: 2. 2005.

 

                   

 

Succulent, usually leafless shrubs or treelets up to 8 m tall, stem diameter to 22 cm, branched; older stems terete, with brownish bark; younger branches smooth, green, distinctly 3(-4)-angled, distinctly articulate with the segments 6-30 by 2-5 cm, drying greenish, with shallow to hardly narrowed sinuses between the spine-shields. Spine-shields in rows, shallow, 1.5-2 cm apart, spines in pairs, (3-)4-6 mm long, blackish, persistent. Indumentum absent. Stipules transformed into spines. Leaves alternate, very soon caducous, not seen on Thai plants and still unknown. Cyathia axillary, yellow, solitary or in dichasia of 3, less than 2 cm long; basal peduncle 4-6 mm long; bracts of branching c. 2 mm long; peduncle of individual cyathia 1 mm (staminate) or 4-6 mm (bisexual cyathia) long; involucral bracts 1.5-2 mm long (2.5-3 mm in fruit); cyathia sessile in involucre; glands 5, transversely elliptic, 1 by 2.5-3 mm, without appendages, insterspersed with erect smaller lobes; pistillate flowers nearly sessile in involucre. Fruits yellow-orange; pedicel 1-3 mm long; schizocarp 4-4.5 by 6.5-7 mm, deeply sulcate and sharply keeled. Seeds c. 2.5 by 2 mm, pale to greybrown, ecarunculate.

    T h a i l a n d.— NORTHERN: Tak (Rahaeng); NORTH-EASTERN: Mukdahan (Mukdahan National Park); EASTERN: Nakhon Ratchasima (Lat Bua Khao); SOUTH-WESTERN: Kanchanaburi (Salakphra), Ratchaburi, Prachuap Khiri Khan (Huai Yang, Hua Hin, Pranburi, Sam Roi Yot); CENTRAL: Saraburi (Phukhae); SOUTH-EASTERN: Chon Buri (Sattahip, Ko Si Chang); PENINSULAR: Phatthalung (Khao Hua Taek), Songkhla (Padang Besar, Sadao).

    D i s t r i b u t i o n.— Described from Malabar and Sri Lanka (lectotype a cultivated plant of unknown origin); current literature cites a range from India to Malesia and China.

    E c o l o g y.— In dry deciduous thickets, on dry rock in evergreen forest, open primary forest; most commonly on limestone hills, but also on sandstone and granite. Altitude: 0-250 m. Flowering: February, May-August, October-December; fruiting: February, April, July, August, November, December (the whole year through?).

    V e r n a c u l a r.— Khia liam (เลี่), ngon ngu (นงู) (Mae Hong Son); khia pha (เ) (Northern); kalam phak (าลพั) (Nakhon Ratchasima); salat dai pa (ลัดได่า) (Central); thu-du-ke-la (ดุละ) (Karen-Mae Hong Son); Malayan spurge tree (English).

    U s e s.— The dried heartwood is antipyretic. The latex is co-carcinogen and is used for the removal of warts.

    N o t e.— This species currently includes trees of c. 8 m as well as tiny shrubs of less than 50 cm height. Herbarium specimens are certainly insufficient, and further field studies are needed to verify if only one species in involved.

 

2. Euphorbia atoto G.Forst., Fl. Ins. Austr.: 36. 1786; Boiss. in DC., Prodr. 15, 2: 12. 1862; Hook.f., Fl. Brit. India 5: 248. 1887; Ridl., Fl. Malay Penins. 3: 181. 1924; Gagnep. in Lecomte, Fl. Indo-Chine 5: 245. 1925; M.R.Hend., Malay. Wild Fl.: 462. 1959; Backer & Bakh.f., Fl. Java 1: 503. 1964; Radcl.-Sm., Kew Bull. 26: 263. 1972; Whitmore, Tree Fl. Malaya 2: 96. 1973; P.H. Hô, Câyco Viêtnam 2, 1: 359, fig. 4566. 1992; J.S. Ma, Fl. Reipubl. Pop. Sin. 44(3): 36, pl. 6 fig. 1-3. 1997; Esser & Chayam., Harvard Papers Bot. 6: 261. 2001; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 268. 2005.— Euphorbia articulata Dennst., Schlüssel Hortus Malab.: 1. Register: 14, 2. Register: 21, 3. Register: 36. 1818, nom. illeg. (non Burm. in Plum., Pl. Amer. 10: 249. 1760); Hook.f., Fl. Brit. India 5: 248. 1887 (as syn. nov.); Binojkumar & N.P.Balakr., Rheedea 3: 113, fig. 1. 1993.— Euphorbia pallens Dillwyn, Rev. Hort. Malab.: 20. 1839.— Euphorbia halophila Miq., Anal. Bot. Ind. 3: 16. 1852; Boiss. in DC., Prodr. 15, 2: 13. 1862; Hook.f., Fl. Brit. India 5: 248. 1887.— Euphorbia atoto G.Forst. var. minor Boiss. in DC., Prodr. 15, 2: 13. 1862.— Chamaesyce atoto (G.Forst.) Croiz. in O.Degener, Fl. Hawaiiensis, Fam. 190, Chamaesyce leafl.: 4. 1936; Florence, Bull. Mus. Nation. Hist. Nat., B, Adansonia 18: 240. 1996.

 

Perennial herb to subshrub with a woody prostrate base and numerous ascending to erect, herbaceous stems to 60 cm tall, shoots distinctly articulate, slightly branched, green to slightly reddish. Indumentum absent. Leaves opposite, more or less distant; interpetiolar stipules completely united, triangular, 1-1.5 by 1-1.5 mm; petioles 1.5-2.5 mm long; blades (ovate-oblong-)elliptic, the largest 17-40 by 9-15 mm and quite uniform in size, thick in texture and fleshy-succulent, base oblique with one side cordate, the other obtuse, margin entire, apex rounded-obtuse and sometimes with a minute mucro, brighter but not whitish beneath, venation very indistinct to invisible, triplinerved, with 6-9 pairs of sideveins. Cyathia grouped to 3-12 in loosely to distinctly clustered, axillary dichasia c. 6-20 mm long, sometimes solitary, pedunculate and subtended by pairs of leafy to linear bracts 4-9 mm long. Involucre 1-1.2 mm long; glands 5 or 4 but sometimes partly absent, 0.5-0.7 mm wide, light green when flowering, reddish-purple in fruit, sometimes shortly stalked, with a minute to absent, pale rim as appendage; ovary with stigmas of 0.6-0.7 mm, apically bifid for less or more than half of their length. Fruits with a pedicel of 2-3 mm, pendent when maturing, erect when mature; schizocarp 2-2.2 by 2.2-3 mm, sulcate. Seeds 1.4-1.5 by 1.1-1.2 mm but often rudimentary to aborted, brown, completely smooth, ecarunculate.

    T h a i l a n d.— SOUTH-WESTERN: Prachuap Khiri Khan (Hua Hin, Huai Yang); SOUTH-EASTERN: Chon Buri (Chomthian, Sattahip, Si Racha), Rayong (Ko Samet), Trat (Ko Chang); PENINSULAR: Chumphon (Ko Tao), Phangnga (Ko Bon), Phuket (Airport Beach, Hat Nai Yang, Laem La, Thalang, Thachuai), Satun (Ko Adang), Songkhla.

    D i s t r i b u t i o n.— From Sri Lanka and India through Burma, Thailand, Indo-China, China up to the Ryukyu Islands of Japan, Malesia, Australia and the S. Pacific (type from Polynesia).

    E c o l o g y.— On sandy beaches and dunes at the seashore, in Casuarina forest. Altitude: near sea level. Flowering and fruiting: the whole year through.

    V e r n a c u l a r.— Ma phrao nok khao (ะำพ้า) (Prachuap Khiri Khan); nam nom ratchasi thale (มร้์ทะ) (Chumphon).

    N o t e s.— This name is well-known, but perhaps has to be replaced by the name of Euphorbia pallens Dillwyn, and further studies are needed (see Esser & Chayam., loc. cit.).

 

3. Euphorbia bifida Hook. & Arn., Bot. Beech. Voy. 5: 213. 1837; Boiss. in DC., Prodr. 15, 2: 25. 1862; J.S.Ma & Z.Y.Wu, Acta Bot. Yunnan. 15: 117. 1991; J.S.Ma, Fl. Reipubl. Pop. Sin. 44(3): 42, pl. 8 fig. 1-4. 1997; Esser & Chayam., Harvard Papers Bot. 6: 261. 2001; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 269, plate XV: 1. 2005.— Euphorbia serrulata Reinw. ex Blume, Bijdr. 12: 635. 1825, nom. illeg. (non Thuill., Fl. Env. Paris ed. 2: 237. 1799); Miq., Fl. Ind. Bat. 1, 2: 421. 1859; Boiss. in DC., Prodr. 15, 2: 25. 1862; Craib, Bull. Misc. Inf. Kew 1911: 456. 1911; Contr. Fl. Siam: 182. 1912; Gagnep. in Lecomte, Fl. Indo-Chine 5: 248. 1925; J.S.Ma & Z.Y.Wu, Acta Bot. Yunnan. 15: 117. 1991 (as syn. nov.).— Euphorbia vachellii Hook. & Arn., Bot. Beech. Voy. 5: 213. 1837; Steenis, Bull. Bot. Surv. India 10: 393. 1968; Radcl.-Sm., Kew Bull. 26: 268. 1972; J.S.Ma & Z.Y.Wu, Acta Bot. Yunnan. 15: 117. 1991 (as syn. nov.); P.H. Hô, Câyco Viêtnam 2, 1: 364, fig. 4680. 1992.— Euphorbia reinwardtiana Steud., Nomencl. Bot. ed. 2, 1: 614. 1840, nom. nov.— Euphorbia coudercii Gagnep., Bull. Soc. Bot. France 68: 299. 1921 & in Lecomte, Fl. Indo-Chine 5: 250, pl. 27 fig. 6-11. 1925; Radcl.-Sm., Kew Bull. 26: 263. 1972; P.H. Hô, Câyco Viêtnam 2, 1: 360, pl. 4670. 1992.— Euphorbia coudercii Gagnep. forma glaberrima Gagnep., Bull. Soc. Bot. France 68: 299. 1921; in Lecomte, Fl. Indo-Chine 5: 251.— Euphorbia harmandii Gagnep., Bull. Soc. Bot. France 68: 299. 1921; in Lecomte, Fl. Indo-Chine 5: 250. 1925, pl. 27 fig. 1-5; Radcl.-Sm., Kew Bull. 26: 264. 1972.— Euphorbia backeri Pax & K.Hoffm., Blumea 3: 60. 1938; Backer & Bakh.f., Fl. Java 1: 504. 1964; Steenis, Bull. Bot. Surv. India 10: 393. 1968.— Chamaesyce vachellii (Hook. & Arn.) Hara, Enum. Spermat. Jap. 3: 44. 1954; Hurus., J. Fac. Sc. Univ. Tokyo, Bot. Ser. 3, 6: 283. 1954.— Chamaesyce harmandii (Gagnep.) Soják, Cas. Nár. Mus., Odd. Prír. 140: 169. 1972.— Chamaesyce coudercii (Gagnep.) Soják, Cas. Nár. Mus., Odd. Prír. 148: 198. 1980 (‘1979’).— Chamaesyce bifida (Hook. & Arn.) T.Kurosawa, Acta Phytotax. Geobot. 51: 212. 2001.— Euphorbia linearifolia auct. non Heyne ex Roth: Hosseus, Beih. Bot. Centralb. 28: 404. 1911; Craib, Contr. Fl. Siam: 182. 1912; Gagnep. in Lecomte, Fl. Indo-Chine 5: 253. 1925; Radcl.-Sm., Kew Bull. 26: 265. 1972.

 

 

Perennial, many-stemmed, mostly erect, branched subshrub to c. 70 cm tall often with a thick, woody rootstock (but sometimes without so). Indumentum distinct to absent on vegetative parts, consisting of brownish-pale hairs, 0.2-1 mm long, weakly erect. Leaves opposite, often only apically; interpetiolar stipules 0.7-1.5 mm long, narrowly triangular, united, apically to deeply bifid, otherwise quite entire; petioles 1-2 mm long; blades narrowly oblong-elliptic to lanceolate (rarely ovate or obovate), 12-35 by 3-7 mm, chartaceous, base oblique with one side cordate, the other side obtuse-rounded, margin entire or completely or only apically serrate, apex mucronate, papillate-hyalin and appearing grey-silvery below, venation very indistinct, slightly triplinerv, with c. 8-10 pairs of side veins. Cyathia 3-10 (or numerous) grouped together in terminal and axillary, dichotomous clusters to 3 cm diameter, often on leafless shoots, glabrous to slightly pubescent, each branching subtended by small leaf-like to linear bracts. Peduncle 2-4 mm long; involucre c. 1 mm long, sometimes apically pubescent; glands 4, 0.5 by 0.7 mm, red-brown, with orbiculate-spathulate, large and corolla-like, pink to white, entire appendages 1-1.5 by 1.5-2 mm; ovary with stigmas of 0.8-1 mm, apically bifid for c. half of their length. Fruits glabrous, with a pedicel of 1-1.5 mm; schizocarp 2-2.25 by 2-2.5 mm, sulcate, sometimes with unequal locules. Seeds 1.4 by 0.8 mm, light brown, not papillate but with numerous, distinct circular depressions, ecarunculate.

    T h a i l a n d.— NORTHERN: Chiang Mai (Doi Kum, Doi Saget, Pa Yo Forest Centre), Phayao (Chiang Muan), Lampang (Doi Khun Tan, Mae Luang, Palat, Chae Hom), Tak (Ban Tak), Phitsanulok (Ban Chang); NORTH-EASTERN: Phetchabun (Nam Nao), Nong Bua Lum Phu, Nakhon Phanom (Tha Uten); EASTERN: Chaiyaphum; SOUTH-WESTERN: Kanchanaburi (Khao Tong), Prachuap Khiri Khan (Sam Roi Yot); SOUTH-EASTERN: Chon Buri (Si Racha, Ko Si Chang); PENINSULAR: Chumphon (Ko Tao), Songkhla (Padang Besar).

    D i s t r i b u t i o n.— Japan (Ryukyu Islands), Taiwan, S. China (types of E. bifida and E. vachellii), Indo-China (types of E. coudercii, E. coudercii forma glaberrima, E. harmandii), Thailand, Malesia (Java-type of E. backeri, Lesser Sunda Islands, Moluccas, Philippines), Solomon Islands, up to N. Australia and the New Hebrides; to be expected in Burma.

    E c o l o g y.— In open grassy ground, dry dipterocarp forest, open deciduous dipterocarp-oak forest, at margin of teak forest, usually exposed and often flowering in leafless forest; on sandy or rocky, often thin soil, granite or limestone bedrock. Altitude: sea level to c. 850 m. Flowering and fruiting: the whole year through.

    V e r n a c u l a r.— Ya kae hak lueang (ีลื) (Lampang); muk bia (ี้) (Nakhon Phanom); muk-noi (น้) (So-Nakhon Phanom).

    N o t e.— This species is extremely variable in vegetative characters, like leaf size and margin and pubescence. Radcliffe-Smith (1972) even noted a close resemblance to African species that should be evaluated in more detail. The record of E. linearifolia was based on the misdetermination of a single collection (Hosseus 709) that is a good match for E. bifida.

 

4. Euphorbia capillaris Gagnep., Bull. Soc. Bot. France 68: 298. 1921; in Lecomte, Fl. Indo-Chine 5: 252. 1925; Radcl.-Sm., Kew Bull. 26: 263. 1972; P.H. Hô, Câyco Viêtnam 2, 1: 359, fig. 4667. 1992; Esser & Chayam., Harvard Papers Bot. 6: 262. 2001; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 270, fig. 68. 2005.— Chamaesyce capillaris (Gagnep.) Soják, Cas. Nár. Mus., Odd. Prír. 140: 169. 1972.— Euphorbia hypericifolia auct. non L.: Hosseus, Beih. Bot. Centralb. 28: 404. 1911; Craib, Contr. Fl. Siam: 181. 1912.

 

 

Herb to 60 cm tall, annual, much-branched, with the ultimate branches very thin and hair-like, entirely green. Indumentum consisting of pale hairs, 0.2-1 mm long, weakly erect, scattered to absent on most parts. Leaves opposite, usually distant; interpetiolar stipules not united, (0.5-)0.8-1.2 mm long, filiform; petioles 1-2 mm long; blades (elliptic-)obovate, the largest 6-25 by 3-14 mm but diminishing in size distally, very thin in texture, base acute (to obtuse) and only slightly oblique, margin entire to shallowly serrate (teeth 0.5-1 mm apart), apex rounded to mucronate, glabrous or with scattered hairs below, distinctly glaucous-whitish below, indistinctly triplinerved, sideveins in 6-7 pairs but hardly visible. Cyathia always solitary in leaf axils, pedunculate and subtended by a pair of small obovate leaves c. 1 mm beneath the cyathium, the peduncles elongating to form additional side branches several cm long with then terminal cyathia, glabrous or with scattered hairs, only the ovaries usually pubescent. Involucre c. 1 mm long; glands 4, 0.2 by 0.4-0.5 mm, with short (to 0.6 mm long), transversely elliptic appendages with undulate to even split margin, i.e. fimbriate; ovary with short (c. 0.5 mm) pedicel, initially distinctly hairy, rarely glabrous; stigmas 0.3-0.5 mm long, bifid c. in upper half and undivided below. Fruits with a pedicel of 0.8-1.5 mm; schizocarp 1.5-1.8 by 2 mm, sulcate, with few scattered hairs, rarely glabrous. Seeds c. 1.4 by 0.9 mm, reddish (meat-coloured), not papillate, with c. 4 distinct, transverse grooves, ecarunculate.

    T h a i l a n d.— NORTHERN: Chiang Mai (W of Bo Luang, Doi Chieng Dao), Lamphun (Doi Khun Tan), Tak (Doi Tung Cha, lectotype: Kao Phra Daeng, hosseus 153, P, isolectotypes BM, K, L, M); EASTERN: Ubon Ratchathani; SOUTH-WESTERN: Kanchanaburi (Erawan National Park, Sai Yok, Sisawat).

    D i s t r i b u t i o n.— Thailand, Laos, Cambodia, Vietnam, to be expected in Burma.

    E c o l o g y.— In open bamboo and deciduous forest, disturbed deciduous dipterocarp-oak forest, roadsides, often on grassy or bare ground, on sandy soil but also on limestone outcrops, granite or limestone bedrock, often not common. Altitude: 250-1,600 m. Flowering and fruiting: (August-)October-February.

    V e r n a c u l a r.— Pom daeng (ดง) (Northern).

 

5. Euphorbia cristata Heyne ex Roth, Nov. Pl. Sp.: 226. 1821; Boiss. in DC., Prodr. 15, 2: 19. 1862; Hook.f., Fl. Brit. India 5: 247. 1887; Radcl.-Sm., Kew Bull. 26: 264. 1972; Esser & Chayam., Harvard Papers Bot. 6: 262. 2001; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 272. 2005.— Euphorbia fimbriata Heyne ex Roth, Nov. Pl. Sp.: 227. 1821, nom. illeg. (non Scopoli, Delic. Fl. Fauna Insubr. 3: 8. 1788); Boiss. in DC., Prodr. 15, 2: 19. 1862; Hook.f., Fl. Brit. India 5: 247. 1887 (as syn. nov.).— Chamaesyce cristata (Heyne ex Roth) G.L.Webster, J. Arnold Arbor. 48: 424. 1967.— Chamaesyce cristata (Heyne ex Roth) Soják, Cas. Nár. Mus., Odd. Prír. 140: 169. 1972, comb. nov. superfl. Euphorbia laciniata Panigrahi, Kew Bull. 30: 531. 1975.

 

Annual herb, prostrate or ascending, branched. Indumentum consisting of pale hairs, (0.5-)1 mm long, loosely erect, on all vegetative parts. Leaves opposite, in dense apical clusters, distantly to absent below; interpetiolar stipules free, c. 1 mm long, linear but with cilia-like lateral lobes, soon caducous; petioles 1-1.5 mm long; blades ovate-elliptic, c. 10 by 7 mm (in the literature given as 15-25 by 8-18 mm), the apical ones often largest, thin, base cordate and hardly oblique, margin entire in lower part, sharply serrate apically, apex rounded-obtuse, distinctly and equally pubescent on both surfaces but often more densely on margins, hardly brighter below, venation distinct, not triplinerved, side veins in c. 3-4 pairs. Cyathia intermingled in and hidden by the apical tuft of leaves, 1-3 per axil. Involucre c. 1.5 mm long, pubescent; glands 4 per cyathium, 0.6-1 mm wide, green, transversely elliptic, appendages very large (1-2.5 by 2-2.5 mm) and leaflike, white, the apical half consisting of 7-11 cilia-like (often?) reddish lobes, apically pubescent but lower part pubescent to glabrous; ovaries with scattered erect hairs, stigmas c. 1 mm long, mostly divided. Fruits with a pedicel of 2 mm; schizocarp c. 1.7 by 2 mm, sulcate, pubescent on the whole surface. Seeds 1.3 by 0.8 mm, brown, not papillate but with 4 distinct, transverse furrows, ecarunculate.

    T h a i l a n d.— NORTHERN: Chiang Mai (Mae Klang Waterfalls, Mae Soi, Muang Hot near Doi Noi); NORTH-EASTERN: Phetchabun (Nam Nao).

    D i s t r i b u t i o n.— Sri Lanka, India (type from ‘India orientalis’), Burma, Thailand.

    E c o l o g y.— In dry deciduous dipterocarp forest, on sunny dry places, on rocks in loamy soil and near streams, on granite. Altitude: 200-500 m. Flowering and fruiting June, November-January.

    V e r n a c u l a r.— Ya nam buek (ญ้าน) (Northern).

    N o t e.— E. cristata belongs to the subsection Elegantes Boiss. All species of this taxon are very similar, and there is disagreement in the literature about species limits. E. cristata is the oldest valid name, but the synonymy could change at further study.

 

6. Euphorbia cyathophora Murr., Comment. Soc. Regiae Sci. Göttingen 7: 81. 1786; Radcl.-Sm., Kew Bull. 32: 75. 1977; in Fl. Pakistan 172: 113. 1986; P.H. Hô, Câyco Viêtnam 2, 1: 357, fig. 4660. 1992; J.S.Ma & C.Y.Wu, Collect. Bot. (Barcelona) 21: 102. 1992; J.S.Ma, Fl. Reipubl. Pop. Sin. 44(3): 65, pl. 17 fig. 1-4. 1997; I.M.Turner, Gard. Bull. Singapore 51: 99. 1999; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 273. 2005.— Poinsettia cyathophora (Murr.) Bartl., Ind. Sem. Hort. Acad. Gött. 1839: 6. 1839; R.L.Dressler, Ann. Missouri Bot. Gard. 48: 338. 1961. Euphorbia heterophylla L. var. cyathophora (Murr.) Griseb., Fl. Br. W. Ind. Isl.: 54. 1859; Boiss. in DC., Prodr. 15, 2: 72. 1862; Christenhusz, Harvard Papers Bot. 7: 5. 2002.Euphorbia heterophylla L. forma cyathophora (Murr.) Voss, Vilm. Blumengärtn. ed. 3, 1: 898. 1896.— Euphorbia heterophylla auct. non L.: Radcl.-Sm., Kew Bull. 26: 264. 1972, p.p.

 

Erect herb to c. 50 cm tall, slightly branched. Indumentum consisting of weakly erect to adpressed, pale hairs to c. 1 mm long, often absent. Stipules c. 0.3-0.5 by 0.7-1 mm, irregularly scaly. Leaves alternate; petioles 0.5-1 cm, often pubescent; blades basically elliptic but often panduriform with 1 or 2 pairs of constrictions, c. 4-9 by 2.5-4 cm, thin, base acute to attenuate, margin indistinctly serrate with teeth 1-2 mm apart, apex acute, at least some leaves deeply red or whitish at base, otherwise green, brighter and initially pubescent below; venation distinct, side veins in 12-15 pairs, not triplinerved, veinlets visible. Cyathia in apical, dichasial clusters, c. 5-6 per group, glabrous; peduncle c. 2.5 mm long; involucre c. 3 mm long; a single gland per cyathium, c. 1.2-1.5 mm in diam., with flattened opening, without appendages; stigmas 1-1.25 mm long, nearly completely bifid. Fruits: pedicel 2.5-3 mm long; schizocarp 3-3.5 by 4.5-5 mm, deeply sulcate, glabrous. Seeds 2.7-3 by 2 mm, apex acute but hardly truncate, surface red-to greybrown, distinctly pustulate and rough, ecarunculate.

    T h a i l a n d.— Usually cultivated, as weed probably collected in PENINSULAR: Chumphon (Pathio), Satun (Ko Adang), Songkhla.

    D i s t r i b u t i o n.— Pantropical garden ornamental and weed, originating from the southern U.S.A., Mexico (type) and Central America.

    E c o l o g y.— Garden escape around habitations, as a weed in open places and on waste ground, collected on limestone. Altitude: 10-50 m. Flowering and fruiting: probably the whole year through.

    V e r n a c u l a r.— Bai tang dok (่างด) (Songkhla); dok-ban-a (าน) (Laos).

    U s e s.— Cultivated as ornamental herb.

 

7. Euphorbia heterophylla L., Sp. Pl.: 453. 1753; Boiss. in DC., Prodr. 15, 2: 72. 1862, p.p. excl. var. cyathophora; Ridl., Fl. Malay Penins. 3: 181. 1924, p.p. excl. E. cyathophora; Gagnep. in Lecomte, Fl. Indo-Chine 5: 244. 1925, p.p. excl. E. cyathophora; Burkill, Dict. Econ. Prod. Malay Pen. 1: 978. 1935; Radcl.-Sm., Kew Bull. 26: 264. 1972, p.p. excl. E. cyathophora; in Fl. Pakistan 172: 112. 1986; P.H. Hô, Câyco Viêtnam 2, 1: 357, fig. 4661. 1992; J.S.Ma, Fl. Reipubl. Pop. Sin. 44(3): 67, pl. 17 fig. 5-8. 1997; I.M.Turner, Gard. Bull. Singapore 51: 99. 1999; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 274, fig. 69. 2005.— Euphorbia geniculata Ort., Nov. Pl. Descr. Dec.: 18. 1797; Boiss. in DC., Prodr. 15, 2: 72. 1862.— Euphorbia prunifolia Jacq., Pl. Hort. Schoenbr. 3: 15, t. 277. 1798; Hook.f., Fl. Brit. India 5: 266. 1887.— Cyathophora heterophylla (L.) Raf., Fl. Tell. 4: 117. 1838.— Poinsettia heterophylla (L.) Klotzsch & Garcke, Monatsber. Akad. Berl. 1859: 253. 1859; R.L.Dressler, Ann. Missouri Bot. Gard. 48: 339. 1961.— Poinsettia geniculata (Ort.) Klotzsch & Garcke, Monatsber. Königl. Preuss. Akad. Wiss. Berlin 1859: 253. 1859.— Poinsettia heterophylla (L.) Klotzsch & Garcke, Monatsber. Königl. Preuss. Akad. Wiss. Berl. 1859: 253. 1859.— Euphorbia heterophylla L. var. prunifolia (Jacq.) Griseb., Fl. Br. W. Ind. Isl.: 54. 1859.— Euphorbia heterophylla L. var. geniculata (Ort.) Gómez, Anal. Hist. Nat. Madrid 23: 46. 1894.

 

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Erect herb up to 1 m tall, stems brown-green, unbranched or with few lateral side-branches or dichotomously branched in upper part. Indumentum distinct to nearly absent, consisting of scattered, weakly erect, pale to 2 mm long. Stipules as indistinct, irregular lobes 0.5-0.8 mm long. Leaves alternate (opposite when dichotomously branching), glabrous to slightly pubescent, dark green and sometimes reddish-maroon throughout, but never with reddish or white base; petioles 1-4 cm long; blades ovate-elliptic or obovate or linear, very rarely panduriform, c. 4-10.5 by 1.1-5 cm, thin, base obtuse to acute with the very base often attenuate, margin entire to subserrate, apex acute to subacuminate, side veins in 12-16 pairs, distinct, not triplinerved. Cyathia c. 10-20 in terminal dichasial clusters, glabrous to pubescent, on peduncles of 1-2 mm. Involucre 2-2.5 mm long; gland solitary, 0.6-0.8 mm wide with circular opening, without appendage; ovary with stigmas of c. 1.25 mm, bifid for c. half length. Fruits: pedicel 1.5-4 mm long; schizocarp c. 3-4 mm long, deeply sulcate, glabrous to slightly pubescent. Seeds 1.8-2.5 by 1.8-2 mm, orbicular-ellipspoid, with truncate apex, surface roughly tuberculate, ecarunculate.

    T h a i l a n d.— Certainly in all provinces, hitherto recorded for NORTHERN: Chiang Mai, Phayao, Lamphun, Lampang, Uttaradit, Tak, Phitsanulok, Kamphaeng Phet; NORTH-EASTERN: Phetchabun, Loei, Nong Khai; EASTERN: Chaiyaphum, Nakhon Ratchasima, Surin, Roi Et, Ubon Ratchathani; SOUTH-WESTERN: Kanchanaburi, Prachuap Khiri Khan; CENTRAL: Lop Buri, Phra Nakhon Si Ayutthaya, Saraburi, Krung Thep, Samut Prakan; SOUTH-EASTERN: Prachin Buri, Sra Kaeo, Chon Buri, Rayong, Chanthaburi; PENINSULAR: Surat Thani, Phuket, Phatthalung, Trang, Songkhla.

    D i s t r i b u t i o n.— Pantropical weed, originating from the New World (type).

    E c o l o g y.— Weed of clearings, plantations, roadsides and waste areas, often on very disturbed places, shady or open, often between grasses, margin of swampy, dry evergreen or deciduous forest, on muddy places, sandy soil, granite or dry limestone hills. Altitude: sea level to 1,100 m. Flowering and fruiting: the whole year through.

    V e r n a c u l a r.— Ya yang (ญ้าาง) (General); ya yang yai (ญ้าางำใญ่) (Loei); bai tang dok (่างด), luk khoei tai mae yai tham sop (ลู) (Central); phak bang yak tang (าง่าง) (Rayong).

 

8. Euphorbia hirta L., Sp. Pl.: 454. 1753, Roxb., Fl. Ind. ed. 1832, 3: 472. 1832; Ridl., Fl. Malay Penins. 3: 181. 1924; Burkill, Dict. Econ. Prod. Malay Pen. 1: 978. 1935; M.R.Hend., Malay. Wild Fl.: 462, fig. 415 A, B. 1959; Radcl.-Sm., Kew Bull. 26: 264. 1972; Whitmore, Tree Fl. Malaya 2: 96. 1973; C.S.Chun, Limestone Fl. Malaya; P.H. Hô, Câyco Viêtnam 2, 1: 361, fig. 4671. 1992; J.S.Ma, Fl. Reipubl. Pop. Sin. 44(3): 44, pl. 8 fig. 5-8. 1997; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 276. 2005.— Euphorbia pilulifera L., Sp. Pl.: 454. 1753, p.p. excl. lectotype; Miq., Fl. Ind. Bat. 1, 2: 420. 1859; Boiss. in DC., Prodr. 15, 2: 21. 1862; Hook.f., Fl. Brit. India 5: 250. 1887; F.N.Williams, Bull. Herb. Boiss., sér. 2, 5: 32. 1905; Gagnep. in Lecomte, Fl. Indo-Chine 5: 245. 1925.— Chamaesyce hirta (L.) Millsp., Publ. Field Columb. Mus., Bot. Ser. 2: 303. 1909.— Euphorbia hirta L. var. typica Wheeler, Contr. Gray Herb. 127: 68. 1939, nom. inval.

 

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Herb, to 45 cm tall, erect to prostrate, branched. Indumentum distinct, consisting of erect, yellow-brown hairs to 1.5 mm long and shorter, adpressed, pale hairs. Stipules free, c. 1 mm long. Leaves opposite; sometimes reddish; petioles 1-2 mm long; blades irregularly ovate-elliptic, c. 1.2-4 by 0.6-1.8 cm, base distinctly oblique, margin serrate with teeth c. 1 mm apart, apex acute, brighter below, side veins 3-5 pairs, distinct, triplinerved. Cyathia green, often tinged reddish, c. 20-50 grouped in axillary capitate clusters [1-3(-6) clusters per axil] with the bracts filiform and 0.5-1 mm long; peduncle of clusters 5-16 mm long; involucre 0.7-0.8 mm long; glands 4, c. 0.1 by 0.15 mm, with narrow, entire appendages c. 0.2 by 0.3 mm; stigmas 0.25-0.3 mm, only slightly bifid apically. Fruits with a pedicel of 0.4-0.5 mm; schizocarp c. 0.9 by 1.2 mm, sulcate, distinctly pubescent on the whole surface. Seeds 0.6-0.7 by 0.5 mm, reddish, smooth, ecarunculate.

    T h a i l a n d.— Certainly in all provinces, hitherto recorded for NORTHERN: Chiang Mai, Chiang Rai, Nan, Lampang, Uttaradit, Phitsanulok, Kamphaeng Phet, Nakhon Sawan; NORTH-EASTERN: Phetchabun, Loei, Nong Bua Lum Phu, Nong Khai, Sakon Nakhon, Nakhon Phanom, Mukdaharn, Maha Sarakham, Khon Khaen; EASTERN: Chaiyaphum, Nakhon Ratchasima, Surin; SOUTH-WESTERN: Kanchanaburi, Phetchaburi, Prachuap Khiri Khan; CENTRAL: Lop Buri, Phra Nakhon Si Ayutthaya, Saraburi, Pathum Thani, Nakhon Nayok, Krung Thep, Samut Prakan; SOUTH-EASTERN: Sa Kaeo, Chon Buri; PENINSULAR: Surat Thani, Trang, Satun, Songkhla.

    D i s t r i b u t i o n.— Worldwide in tropical and subtropical regions, and probably of American origin but naturalized in Asia (up to China) for a long time (type of unknown origin).

    E c o l o g y.— One of the most common weeds in Thailand, at roadsides, railway lines, on clearings, in plantations and rice fields, disturbed evergreen, dry deciduous and swampy forests, open grassland, along streams, often on heavily disturbed places with severe trampling, usually sunny and exposed; on sandy soil, limestone, granite or concrete. Altitude: sea level to 1,200 m. Flowering and fruiting: the whole year through.

    V e r n a c u l a r.— Ya nam muek (ญ้าน้หม) (Northern); ya-lang-ueng (ญ้าลังึ่ง) (Shan-Mae Hong Son); nam nom ratchasi (มร้์), nom ratchasi (มร้์), phak khom daeng (กโดง) (Central); Garden spurge (English).

    U s e s.— The juice of fresh stem or leaves is put directly on fresh or infected wounds by the Karen. A decoction of dried and boiled plants is drunken for stomach and intestinal ulcers (White Mong).

 

9. Euphorbia lacei Craib, Bull. Misc. Inf. Kew 1911: 456. 1911; Contr. Fl. Siam: 182. 1912; Gagnep. in Lecomte, Fl. Indo-Chine 5: 255. 1925; Radcl.-Sm., Kew Bull. 26: 265. 1972; Kiew, Gard. Bull. Singapore 50: 192. 1998; Esser & Chayam., Harvard Papers Bot. 6: 262. 2001; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 276, fig. 70. 2005.— Euphorbia trigona Roxb., (Hort. Beng.: 36. 1814, nom. nud.) Fl. Ind. ed. 1832, 3: 468. 1832, nom. illeg. (non Mill., Gard. Dict. Ed. 8: Euphorbia number 3. 1768); Wight, Icon. Pl. Ind. Orient. 5, 2: t. 1863. 1852; Hook.f., Fl. Brit. India 5: 256. 1887.— Euphorbia barnhartii Croizat, Euphorb. Antiq.: 54. 1934, nom. nov.; Backer & Bakh.f., Fl. Java 1: 501. 1964; Radcl.-Sm., Kew Bull. 26: 263. 1972.

 

 

Succulent, usually leafless shrub/tree up to 8 m tall, stem dark green, branching throughout, up to 19 cm diam.; bark thin, smooth, green and turning grey to brownish; oldest stems terete, branches curving outwards and often scrambling, younger branches 3(-4)-angled, characteristically grey-green when dry, up to 50 by 3(-4) cm without articulation, with a fleshy, terete center 5-10 mm in diam. and with 3(-4) narrow to distinct wings c. 5-10 mm wide, with shallow to very deep sinuses between the spine-shields. Spine-shields massive, spine-shields (1.5-)2.5-4.5 cm apart, spines in pairs, 2-3 mm long (6-7 mm incl. spineshield), reddish-maroon and drying greyish-to yellowish-brown, soon caducous. Indumentum absent. Stipules transformed into spines. Leaves alternate; petiole 6-7 mm long; blade obovate-elliptic, (3-)5.5-10.5 by (1.5-)4-4.5 cm, membranous, base obtuse, margin entire, apex rounded to mucronate. Cyathia green with yellow glands and staminate flowers, axillary, solitary or in a dichasium of 3 cyathia, 0.7-2 cm long; basal peduncle 2.5-4 mm long; bracts of branching 1.5-2 mm long; peduncle of individual cyathia 1-2 mm (staminate) or 5-16 mm (bisexual cyathia) long; involucral bracts c. 2 (staminate) -5 (bisexual cyathia) mm long; bisexual cyathia sessile, involucre c. 3 mm long, staminate cyathia with a peduncle c. 1 mm long; involucre 1.5-2.5 mm long, glands 5, transversely elliptic, 1.5-2 by 2-3.5 mm, without appendages, interspersed with 1.5 mm long, apically ciliate lobes; stigma of pistillate flowers c. 1.5 mm long, only apically divided. Fruits dull red; pedicel 5-8 mm long; schizocarp 5-6 by 12-15 mm, deeply sulcate and sharply keeled; remaining columella 5-5.5 mm long. Seeds 3.25-3.5 by 2.5-3 mm, light-brown to white, smooth, ecarunculate.

    T h a i l a n d.---NORTHERN: Chiang Mai (Doi Sutep, Muang Khong above the Mae Taeng River, Pa Pae near Mae Taeng), Nan (Shaehaeng Arboretum), Lamphun (Mae Tha; lectotype: kerr 1018, K, isolectotypes BM, TCD), Lampang (Chae Son National Park), Sukhothai (Muang Kao Distr.); NORTH-EASTERN: Sakon Nakhon (Phu Phan National Park); EASTERN: Chaiyaphum (Phu Khiao); SOUTH-WESTERN: Kanchanaburi (Thung Yai Naresuan Wildlife Sanctuary, Wangka); CENTRAL: Saraburi (Sam Lan); SOUTH-WESTERN: Trat (Ko Chang); PENINSULAR: Nakhon Si Thammarat (Thung Song).

    D i s t r i b u t i o n.— Burma, Thailand, Java, Borneo (Sabah), Lesser Sunda Islands, Philippines, perhaps also India.

    E c o l o g y.— Along streamlets and in degraded deciduous or disturbed evergreen/deciduous hardwood forest, often on rocky terrain, on granite or limestone, exposed or shaded. Altitude: 125-900 m. Also cultivated as a hedge plant in Chiangmai province (coll. Kerr 3528) and Bangkok (coll. Kerr 6750). Flowering January-April, fruiting March and April.

    V e r n a c u l a r.— Khia pha (เ) (Northern); salatdai khao (ลัดได), som chao (้า) (Central).

    N o t e.— The species known in India as E. barnhartii (= E. trigona Roxb.) is probably conspecific with E. lacei (see Esser & Chayam. 2001).

 

10. Euphorbia parkeri Binojkumar & N.P.Balakr., Kew Bull. 48: 795, fig. 1. 1993; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 277. 2005.

 

Subshrub up to 30 cm tall, with thick woody rootstock, distinctly branched; light green to dull reddish. Indumentum absent. Leaves opposite; interpetiolar stipules c.1 mm long, united; petioles c. 1-1.5 mm long; blades obovate-elliptic, the largest ones 9-11 by 4-5 mm, base slightly oblique with an obtuse and a subcordate side, margin serrate in upper part, apex rounded-mucronate,slightly brighter below, triplinerved, side veins in c. 3 pairs. Cyathia grouped to few (c. 3) in terminal and subterminal subsessile dichasia, the bracts leaf-like. Involuvcre c. 1 mm long; glands 4, c. 0.6 mm wide, with nearly orbicular, white, entire appendages of 0.8 by 1.1 mm; ovary on short (c. 0.5 mm long) pedicel, stigmas 0.6-0.7 mm long, deeply bifid. Fruits: pedicel c. 0.5-1 mm long; schizocarp 1.8-2 by 2 mm, sulcate. Seeds c. 1.2 by 0.8 mm, brownish, not papillate but with distinct transverse furrows, ecarunculate.

    T h a i l a n d.---NORTHERN: Mae Hong Son (Mae Sam Lap along the Salawin River).

    D i s t r i b u t i o n.----Burma (type), Thailand.

    E c o l o g y.— Temporarily inundated river floodplains, between basalt rocks. Altitude: 150 m. Flowering and fruiting: March.

    V e r n a c u l a r.— Salat dai salawin (ลัดไดาละำ) (Mae Hong Son).

    N o t e.— A new record for Thailand, and the single collection (Maxwell 89-289) perhaps the second record of this species available at all.

 

11. Euphorbia parviflora L., Syst. Nat. ed. 10: 1047. 1759, nom. cons. prop.; Burm.f., Fl. Ind.: 112. 1768; Boiss. in DC., Prodr. 15, 2: 20. 1862; Hook.f., Fl. Brit. India 5: 250. 1887; Thell. in Asch. & Gräbner, Syn. Mitteleur. Fl. 7(92): 436. 1917; Gagnep. in Lecomte, Fl. Indo-Chine 5: 247. 1925; Raju & Rao, Indian J. Bot. 2: 204. 1979; Esser & Chayam., Harvard Papers Bot. 6: 263. 2001; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 279. 2005.— Euphorbia pilulifera L., Sp. Pl.: 454. 1753, p.p. as to lectotype, nom. rejic. prop.; L.C.Wheeler, Contr. Gray Herb. 127: 78. 1939; Esser & Cafferty, Taxon 50: 925. 2001.— Euphorbia papilligera Boiss., Cent. Euph.: 8. 1860.— Chamaesyce pilulifera (L.) Small, Fl. SE. U.S.: 708. 1903.— Euphorbia hypericifolia L. var. parviflora (L.) Prain, Bengal Pl. 2: 924. 1903.— Chamaesyce parviflora (L.) Soják, Cas. Nár. Mus., Odd. Prír. 140: 169. 1972.— Euphorbia hypericifolia auct. non L.: Hook.f., Fl. Brit. India 5: 249. 1887, p.p.; Backer & Bakh.f., Fl. Java 1: 501. 1964, p.p.; Radcl.-Sm., Kew. Bull. 26: 265. 1972; ?J.S. Ma, Fl. Reipubl. Pop. Sin. 44(3): 41. 1997.— Euphorbia indica auct. non Lam.: ?Gagnep. in Lecomte, Fl. Indo-Chine 5: 248. 1925; ?P.H. Hô, Câyco Viêtnam 2, 1: 361, fig. 4673. 1992.

 

Herb to 65 cm tall, erect or not hardly branched, with ultimate branches not notably thin, green to reddish-brown. Indumentum consisting of pale hairs, 0.2-1.2 mm long, weakly erect to loosely appressed, distinct to scattered on vegetative parts, short (c. 0.2 mm) on the stems, usually longer on leaves. Leaves opposite, usually distant, glabrous to pubescent; interpetiolar stipules not united, 0.2-0.8 mm long, broadly triangular; petioles 1.5-2 mm long; blades ovate-elliptic to obovate-elliptic, the largest 13-28 by 6-13 mm and hardly diminishing in size distally, base very oblique with one side cordate, the other obtuse to acute, margin subentire to distinctly serrate, apex rounded to mucronate, glabrous above, usually with scattered hairs below, brighter but not whitish below, triplinerved, with 5-7 pairs of veins. Cyathia always grouped to 5-30 in loosely clustered, axillary dichasia, pedunculate and subtended by pairs of linear bracts 1-1.5 mm long, rarely on elongating peduncles, glabrous or with scattered hairs (ovaries always pubescent). Involucre c. 1 mm long; glands c. 0.2 mm wide, pink, with large (c. 0.4 by 0.7 mm), transversely elliptic, entire and undivided appendages; ovary with short (c. 0.5 mm) peduncle, distinctly hairy; stigmas c. 0.4 mm long, at least for half of their length, often nearly completely bifid. Fruits with a pedicel of 0.5-0.8 mm; schizocarp 1.1-1.5 mm long, sulcate, with scattered hairs on the whole surface. Seeds c. 0.8-1 by 0.6-0.8 mm, yellowish-to medium-brown, smooth to slightly roughened, often with c. 3 very shallow and indistinct grooves, ecarunculate.

    T h a i l a n d.— NORTHERN: Mae Hong Son (15 km NW of Mae Hong Son), Chiang Mai (Ban San Ba Sak, Doi Muang Awn, Mae Heeyah, Mae Soi), Lamphun (Me Li), Lampang (Ban Nikom, Mae Mawh, Mae Wang, Muang Ngao, Doi Pang La, Huay Tak), Phrae (Mae Yom National Park), Tak (Doi Tung Cha, Raheng); NORTH-EASTERN: Nong Khai (Chaiyaburi), Nakhon Phanom, Mukdahan; SOUTH-WESTERN: Kanchanaburi (Wangka); CENTRAL: Chai Nat, Ang Thong, Bangkok.

    D i s t r i b u t i o n.— Uncertain, because most data in the literature are based on confusion with similar species; probably from Sri Lanka (type) and India to Nepal, Burma and Indo-China, data on China and Malesia uncertain but at least on Java.

    E c o l o gy.— In open grassland at solfatara, in rice and soybean fields, light roadside forest, degraded seasonally deciduous hardwood-bamboo forest, teak and bamboo forest, on grassy or swampy ground, sandy river bank, on granite or limestone bedrock. Altitude: 50-500 m. Flowering and fruiting: probably the whole year through.

    V e r n a c u l a r.— Buea daeng (เื้ดง) (Northern); nam nom ratchasi (มร้์) (Central).

    N o t e.— E. parviflora has been confused with E. hypericifolia for a long time. E. hypericifolia is a completely glabrous species indigenous to the New World, and not found in Thailand. The seeds of E. parviflora may be completely smooth (e.g., coll. Wichian 320), or having shallow grooves and ridges in otherwise identical plants (e.g. coll. Maxwell 91-935); this character does not seem reliable to separate E. parviflora from related species (such as E. indica Lam.). The collection Put 2074 (Aranya Prathet, Sra Kaeo province) is more densely pubescent throughout, with larger leaves (3.3 by 1.4 cm) and notably larger fruits (2.0 mm long), and therefore approaches E. indica. Seed surface, leaf shape etc. do not differ from other Thai plants. Nomenclatural problems have been discussed in two separate publications (Esser & Cafferty, loc. cit.; Esser & Chayam., loc. cit.).

 

12. Euphorbia prolifera Buch.-Ham. ex D.Don, Prodr. Fl. Nepal.: 62. 1825; Hook.f., Fl. Brit. India 5: 264. 1887; Radcl.-Sm., Kew Bull. 26: 266. 1972; J.S.Ma, Fl. Reipubl. Pop. Sin. 44(3): 118, pl. 39 fig. 1-4. 1997; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 280. 2005.— Euphorbia nepalensis Boiss. in DC., Prodr. 15, 2: 157. 1862, nom. illeg. (nom. nov. superfl.).— Tithymalus proliferus (Buch.-Ham. ex D.Don) Soják, Cas. Nár. Mus., Odd. Prír. 140: 175. 1972.— Euphorbia himalayensis auct. non Boiss.: Gagnep. in Lecomte, Fl. Indo-Chine 5: 244. 1925.

 

Euphpros-ph1.jpg (303694 bytes)

 

Erect perennial subshrub, c. 50 cm tall, with several unbranched stems arising from a woody rootstock, the apical flower-bearing branches in a whorl 4-6. Indumentum absent. Leaves alternate in vegetative parts, the bracts of the floriferous branches in a whorl of 4-6, the leaves of the floriferous branches opposite; stipules absent; petioles nearly absent; blades linear, 20-22 by 2-4 mm (the leaves of the floral branches elliptic, c. 10 by 5 mm), base obtuse, margin entire and revolute, apex obtuse with a short mucro, brighter but not glaucous below, venation nearly invisible. Cyathia terminal, solitary at the end of each branch, surmounted by a pair of leaf-like bracts. Glands 4, falciform, without appendages; ovaries with 3 carpels. Fruits with a pedicel of c. 5 mm; schizocarp c. 4.5 by 4 mm, 3-locular. Seeds unknown for Thailand, outside of Thailand c. 3 by 2 mm, brown, smooth, ecarunculate.

    T h a i l a n d.---NORTHERN: Mae Hong Son (Kun Yuam).

    D i s t r i b u t i o n.— Himalaya (type: Nepal) to Laos and China.

    E c o l o g y..— In Dipterocarp and Pine forest. Altitude: 600 m. Flowering: May.

    V e r n a c u l a r.— Salat dai khun yuam (ลัดได) (Northern).

    N o t e.— The only Thai collection (Kerr 5454) is rather poor with fruits only. Besides carpel number, woody rootstock and perhaps the absent caruncle of the seeds, it is hardly distinguishable from E. saxicola.

 

13. Euphorbia prostrata Aiton, Hort. Kew. ed. 1, 2: 139. 1789; Boiss. in DC., Prodr. 15, 2: 47. 1862; Hook.f., Fl. Brit. India 5: 266. 1887; Radcl.-Sm., Kew Bull. 26: 266. 1972; Backer & Bakh.f., Fl. Java 1: 503. 1964; P.H. Hô, Câyco Viêtnam 2, 1: 362, fig. 4675. 1992; J.S.Ma, Fl. Reipubl. Pop. Sin. 44(3): 51, pl. 10 fig. 5-8. 1997; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 281. 2005.— Chamaesyce prostrata (Aiton) Small, Fl. S.E. U.S.: 713. 1903.— Euphorbia thymifolia auct. non L.: P.H. Hô, Câyco Viêtnam 2, 1: 363, pl. 4679. 1992, p.p.

 

Prostrate to partly erect annual herb, up to c. 15 cm tall, many-stemmed with stolons, in upper part with short axillary shoots; dark green to partly reddish. Indumentum consisting of pale, erect hairs, 0.1-0.2 mm long, on the stems often in a narrow bands only. Leaves opposite; interpetiolar stipules united, 0.3-0.7 mm long, triangular and entire, sometimes apically bifid to divided; petioles 0.5-1 mm; blades broadly obovate-elliptic, the largest 3.5-6 by 2-5 mm and quite homogeneous in size, base slightly oblique with one side subcordate, the other side obtuse, margin shallowly serrate apically, apex rounded to submucronate, below greyish in living ones, but hardly brighter when dried, glabrous above, with erect hairs only distally below, venation very indistinct to invisible, triplinerved, with 4-5 pairs of side veins. Cyathia pinkish with purple glands, few (2-c. 4) grouped in axillary dichasia, interspersed with distinct, leaf-like pairs of bracts each c. 1-2 by 0.7-1.2 mm and apicall hairy, often elongating to short axillary shoots, glabrous or with rows of hairs. Involucre on a peduncle of 1 mm above the last pair of bracts, 0.7-0.8 mm long, glabrous or distally with scattered hairs; glands 4, c. 0.1 mm wide, stalked, with minute to lacking appendages; ovary distinctly pubescent; stigmas 0.2-0.3 mm long, divided for half or more of their length but not completely. Fruits with a pedicel of 0.5-1.2 mm; schizocarp 1.1-1.2 by 1.2-1.3 mm, sulcate and sharply keeled, partly glabrous but with erect hairs on keels. Seeds c. 0.9 by 0.6 mm, reddish-, yellow-to pale brown, not papillate but with (4-)5 distinct, transverse grooves, ecarunculate.

    T h a i l a n d.— Probably throughout Thailand but only rarely collected. NORTHERN: Chiang Mai; SOUTH-WESTERN: Kanchanaburi (Sai Yok), Prachuap Khiri Khan; CENTRAL: Phra Nakhon Si Ayutthaya (Ayutthaya); Bangkok (Chatuchak); SOUTH-EASTERN: Chon Buri (Koh Si Chang); PENINSULAR: Phatthalung (Kao Pu-Kao Ya National Park), Songkhla (Hat Yai).

    D i s t r i b u t i o n.---Originating from tropical America (type: cultivated at Kew but originating from the West Indies), and now widespread and naturalized in tropical, subtropical and mediterranean regions around the earth, in Asia up to Nepal and China.

    E c o l o g y.---Weed in disturbed open areas, gardens, pathsides, in rocky ruderal places in cultivated areas with patchy annual vegetation and regular but not heavy trampling; sandy earth, granite or limestone bedrock. Altitude: sea level to c. 300 m (for other regions cited up to 1,200 m). Flowering and fruiting: probably the whole year through.

    V e r n a c u l a r.— Ya rok (ญ้า) (General).

 

14. Euphorbia pulcherrima Willd. ex Klotzsch, Neue Allg. Deutsche Garten-Blumenzeitung 2: 27. 1834; Boiss. in DC., Prodr. 15, 2: 71. 1862; Kurz, Forest Fl. Burma 2: 418. 1877; Ridl., Fl. Malay Penins. 3: 182. 1924; Gagnep. in Lecomte, Fl. Indo-Chine 5: 243. 1925; Burkill, Dict. Econ. Prod. Malay Pen. 1: 980. 1935; P.H.Hô, Câyco Viêtnam 2, 1: 357, fig. 4659. 1992; J.S.Ma, Fl. Reipubl. Pop. Sin. 44(3): 63, pl. 16 fig. 1-3. 1997; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 281. 2005.— Poinsettia pulcherrima (Willd. ex Klotzsch) Graham, Edinb. New Philos. J. 20: 412. 1836; Bot. Mag. 63: tab. 3493. Dec. 1836; R.L.Dressler, Ann. Missouri Bot. Gard. 48: 335. 1962.

 

Shrub 3 m tall, stem diameter 8 cm, not to slightly branched, as seedling with a fleshy storage root; bark light brown, smooth, branchlets hollow. Indumentum consisting of pale-brownish hairs, to c. 1 mm long, loosely erect. Leaves alternate, green; stipules as small scales, caducous; petioles c. 5-7 cm long, subglabrous; blades ovate-elliptic and sometimes panduriformly lobed, c. 12-17 by 6-9 cm, chartaceous, base acute or obtuse with very base acute, margin entire, apex acuminate, glabrous above, slightly brighter and distinctly pubescent below, venation distinct, not triplinerved, with c. 16-17 pairs of sideveins. Cyathia grouped in an apical pseudo-umbel, glabrous, their bracts enlarged, leaflike, with a pedicel of 1-3 cm, narrower than stem-leaves, green with red midrib or completely red; peduncles 4-5 mm long; involucres c. 5 by 4-5 mm; gland 1, c. 5 mm wide, without appendage; ovary with a pedicel of c. 3 mm, stigmas united into a style column of 1-5 mm, free stigmas completely bifid. Fruits not studied, but described as green, sulcate, with a somewhat fleshy pericarp. Seeds not studied, described as 10 mm long, smooth.

    T h a i l a n d.— Widely cultivated and often escaping, naturalizing at least in NORTHERN: Chiang Mai (Doi Sutep).

    D i s t r i b u t i o n.— Originating from Mexico (type), and now widely cultivated in tropical and subtropical regions around the earth. Flowering January, February, September.

    E c o l o g y.— Escaped garden ornamental, along roadsides; originally (Mexico) found in tropical deciduous forest. Altitude: c. 1,000 m.

    V e r n a c u l a r.— Ban bai (านใ) (Northern); khritsamat (ริสมิส) (Ratchaburi); pho phan (ัน), song radu (ระำดู) (Bangkok); Apha-nay (Akha-Chiang Rai); Poinsettia (English).

    U s e s.— Widely cultivated as ornamental. In Java the leaves are eaten as seasoning (Burkill, loc. cit.).

 

15. Euphorbia reniformis Blume, Bijdr. 12: 634. 1825; Miq., Fl. Ind. Bat. 1, 2: 421. 1859; Boiss. in DC., Prodr. 15, 2: 20. 1862; Craib, Bull. Misc. Inf. Kew 1911: 456. 1911; Contr. Fl. Siam: 182. 1912; Gagnep. in Lecomte, Fl. Indo-Chine 5: 251. 1925; Radcl.-Sm., Kew Bull. 26: 266. 1972; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 282. 2005.— ?Euphorbia congenera Blume, Bijdr. 12: 634. 1825; Miq., Fl. Ind. Bat. 1, 2: 421. 1859; Boiss. in DC., Prodr. 15, 2: 22. 1862; F.N.Williams, Bull. Herb. Boiss., sér. 2, 5: 32. 1905; Craib, Bull. Misc. Inf. Kew 1911: 456. 1911, Contr. Fl. Siam: 182. 1912.— Chamaesyce reniformis (Blume) Soják, Cas. Nár. Mus., Odd. Prír. 148: 199. 1980 (‘1979’).— Euphorbia hypericifolia auct. non L.: Backer & Bakh.f., Fl. Java 1: 501. 1964, pro parte.

 

Prostrate to partly erect, annual to perennial herb up to. c. 30 cm tall, slightly branched, with tap roots (stoloniferous?), stem and parts of leaves purplish. Indumentum consisting of pale hairs, 0.2-0.8 mm long, erect, scattered to dense on all surfaces. Leaves opposite, quite distant; interpetiolar stipules not united above but sometimes united below, 0.5-1 mm long, mostly divided into few ciliae; petioles 1.5-2.5 mm long; blades broadly ovate-elliptic, the largest 10-14 by 6-8 mm and quite homogeneous in size, base very oblique with one side cordate, the other side acute, margin entire to serrate (teeth 0.5-1 mm apart), apex rounded with a tiny mucro, evenly pubescent on both surfaces, slightly brighter below, venation very indistinct, triplinerv, with 4-5 pairs of side veins. Cyathia always grouped c. 5-15 in loosely to densely clustered, axillary dichasia, with a basal peduncle of at least 2 mm but later elongating and then with leaves, bracts linear, 0.7-1 mm, long, pubescent throughout. Involucre c. 0.7 mm long, sparsely pubescent; glands 4, c. 0.1 mm wide, pink to purplish, with large (0.2-0.4 by 0.4-0.7 mm), transversely elliptic, white, undivided appendages; ovary densely hispid-pubescent; stigmas c. 0.4 mm long, mostly divided. Fruits with a pedicel of 0.7-1.5 mm; schizocarp 1.2-1.3 by 1.5 mm, sulcate, distinctly pubescent on the whole surface. Seeds 0.9-1 by 0.7-0.8 mm, brown, smooth, neither papillate nor grooved, ecarunculate.

    T h a i l a n d.— NORTHERN: Lampang (S. of Thoen); CENTRAL: Saraburi (Phra Putthabat), Nakhon Nayok (Khao Yai), Nakhon Pathom (Salaya), Pathum Thani, Bangkok, Samut Prakan (Ban Bang Pu Kao).

    D i s t r i b u t i o n.— Thailand, Java (type), Lesser Sunda Islands.

    E c o l o g y.— Weed on roadsides, railway embankments and in gardens and waste grounds, on open rocky slopes, in sunny places. Altitude: sea level to c. 750 m. Flowering and fruiting: probably the whole year through.

    V e r n a c u l a r.— Buea num (เื้) (General).

 

16. Euphorbia ridleyi Croizat, Gard. Bull. Singapore 9: 147. 1937; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 283. 2005.— Euphorbia synadenium Ridl., J. Straits Branch Roy. Asiat. Soc. 61: 36. 1912; Fl. Malay Penins. 3: 180. 1924 (non Euphorbia synadenia Baill., Adansonia 3: 142. 1862-63); Burkill, Dict. Econ. Prod. Malay Pen. 1: 980. 1935; Radcl.-Sm., Kew Bull. 26: 267. 1972; Whitmore, Tree Fl. Malaya 2: 96. 1973.

 

Erect shrub, to 60 cm tall (to 1.5 m tall fide Croizat, loc. cit.), unbranched, with thick, slightly succulent stem (to 8 mm diam.). Indumentum absent. Leaves alternate, often absent in lower part; stipules irregularly triangular, 0.3-0.5 mm long, undivided; petioles to 10-15 mm long (to 35 mm long fide Croizat); blades obovate, 9-13 by 4-6.5 cm (to 21 by 7 cm fide Croizat), slightly succulent, base narrowly acute and narrowed into the petiole, margin entire, apex rounded to subacute, slightly brighter below, midrib thick but additional venation very indistinct, not triplinerved, side veins in c. 9 pairs. Cyathia solitary in the axils of upper leaves (or paired fide Croizat), only staminate ones seen, green, with a peduncle of 2-4 mm; involucral bracts 2-2.5 mm long, yellow or pinkish; glands 4-5, transversely elliptic, c. 2 mm wide, dark yellow, without appendages. Pistillate flowers not studied, still undescribed. Fruits not studied, but described by Croizat (loc. cit.) as having a distinct pedicel (pedicel and peduncle together 8 mm long), 8 by 13 mm, sulcate, with stigmas completely divided. Seeds not studied, still undescribed.

    T h a i l a n d.— PENINSULAR: Surat Thani (Phanom), Nakhon Si Thammarat (Khao Luang, Khao Rum), Yala (Banang Sata).

    D i s t r i b u t i o n.— Malay Peninsula (excluding Singapore; type), Thailand.

    E c o l o g y.— Epilithic on streamsides, in evergreen forest along waterfall, or on rocky place near river in shaded primary evergreen forest. Altitude: 50-400 m. Flowering: February, May, July, October, November.

    V e r n a c u l a r.— Plao ka (เล้า), rak luk ma (ลูหม) (Peninsular).

    U s e s.— Used as medicine for poulticing burns.

    N o t e s.— Ridley, when describing the species as E. synadenium, was aware that the older name E. synadenia Baill. existed, but considered both name as distinct enough to be valid. Croizat (loc. cit.) disagreed and published a new name (E. ridleyi). He mentioned that Baillon’s name of Euphorbia synadenia, describing an African species, has been erroneously cited as ‘synadenium’ in the literature, and therefore the risk of confusion exists. The ICBN is quite vague on the matter of confusingly similar names (Art. 53.3), but I feel that use of Croizat’s name, E. ridleyi, avoids any doubts and is preferred here.

 

17. Euphorbia saxicola Radcl.-Sm., Kew Bull. 25: 552. 1971; Kew Bull. 26: 267. 1972; Hooker’s Icon. Pl. 38: tab. 3725. 1974; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 284. 2005.— Tithymalus saxicolus (Radcl.-Sm.) Soják, Cas. Nár. Mus., Odd. Prír. 148: 199. 1980 (‘1979’).

 

Erect annual herb to c. 45 cm tall, slightly woody but without a woody rootstock, the vegetative part mainly unbrached or with very short axillary sidebranches, but the apical flower-bearing branches in a whorl of (3-)4 and up to 5 cm long. Indumentum absent. Leaves alternate in vegetative part, the bracts of the floriferous branches in a whorl of (3-)4, the leaves of the floriferous branches opposite; stipules absent; petioles c. 0.5 mm long (absent in floral region); blades narrowly obovate-elliptic, 30-40 by 5-8 mm (the leaves of the floral branches however ovate-elliptic, 9-14 by 7-9 mm), thin, base acute, margin entire, apex acute with a short mucro, slightly glaucous below, venation quite indistinct, not triplinerved, side veins in 10-15 pairs. Cyathia solitary at the apex of a shoot segment, with a peduncle of 1-2 mm, surmounted by a pair of leaf-like bracts. Involucre c. 1.5-2 mm long, glands 4, c. 0.5 by 1 mm, falciform w, their elongate protrusions 0.8 mm long, shortly stalked, without appendages; ovaries with 2 (rarely 3) carpels; stigmas 2, c. 1.5 mm long, apically bifid for c. half of their length or less. Fruits with a pedicel of 2-4 mm; schizocarp 4-4.5 by 5 mm, 2(-3)-locular, sulcate. Seeds 3 by 2 mm, brown, neither papillate nor furrowed, with a distinct caruncle of 0.7 by 1 mm.

    T h a i l a n d.— NORTHERN: Chiang Mai (Doi Chieng Dao, type: kerr 6598, holotype K, isotypes BK, BM).

    D i s t r i b u t i o n.— Endemic.

    E c o l o g y.— On grassy and rocky mountain slopes and ridges, among rocks and on open rocky ground, on limestone. Altitude: 1,800-2,100 m. Flowering and fruiting August-November.

    V e r n a c u l a r.— Nam nom chiang dao (งดา) (Chiang Mai)

    N o t e s.— Radcliffe-Smith, when describing E. saxicola and also in 1974, distinguished E. saxicola from related Himalayan species mainly by two characters, namely annual habit and, among the annual species, being the only one with smooth seeds. The 2-locular and 2-seeded fruits are perhaps even more diagnostic, although very rarely single fruits with 3 carpels occur (coll. Smitinand & Sleumer 1086). Compare also the notes on E. prolifera.

 

18. Euphorbia serpens  Kunth in Humb., Bonpl. & Kunth, Nov. Gen. Sp. 2: 41 (folio), 52 (quarto). 1817; Boiss. in DC., Prodr. 15, 2: 29. 1862, p.p. (excl. var. indica); Radcl.-Sm., Kew Bull. 32: 75, 76. 1977; J.S. Ma, Fl. Reipubl. Pop. Sin. 44(3): 47, pl. 9 fig. 7-12. 1997; Hügin, Feddes Repert. 109: 509. 1998; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 284. 2005.— Euphorbia orbiculata Miq., Fl. Ind. Bat. 1, 2: 421. 1859, nom. illeg. (non Kunth in Humb., Bonpl. & Kunth, Nov. Gen. Sp. 2: 52. 1817); Backer & Bakh.f., Fl. Java 1: 503. 1964; P.H. Hô, Câyco Viêtnam 2, 1: 362, fig. 4674. 1992.— Chamaesyce serpens (Kunth) Small, Fl. SE. US.: 709. 1903.— Euphorbia orbiculata Kunth var. jawaharii Rajagopal & Panigrahi, Taxon 17: 547. 1968.— Euphorbia microphylla auct. non Heyne ex Roth: Gagnep. in Lecomte, Fl. Indo-Chine 5: 252. 1925; Radcl.-Sm., Kew Bull. 26: 266. 1972.

 

Loosely prostrate to partially erect annual herb, up to c. 20 cm tall, much-branched with branches often zig-zag but not forming dense mats, often rooting at nodes, fragile and easily disintegrating; light green to green, only rarely with a reddish touch. Indumentum absent. Leaves opposite; interpetiolar stipules united, 0.4-0.6 mm long, triangular and sometimes apically slightly bifid to denticulate, whitish and therefore very distinct; petioles 0.2-0.7 mm long; blades broadly elliptic (rarely ovate), the largest 2.5-4 by 2-3 mm, base oblique with one side subcordate and one side acute, or symmetrical with both sides obtuse-subcordate, margin entire or indistinctly serrate, apex emarginate, slightly brighter below, venation very indistinct, triplinerved, with 3-4 pairs of side veins. Cyathia solitary, terminating axillary shoots and solitary in the axils of apical leaves, without any typical bracts, on a peduncle of 0.8-1 mm. Involucre c. 0.75 mm long; glands 4, 0.15-0.2 mm wide, purple, sessile, appendages 0.2 by 0.3-0.5 mm, white, undivided to shallowly 2-3-lobulate; stigmas 0.25-0.3 mm long, completely divided. Fruits with a pedicel of 0.3-1.5 mm; calyx present and distinct; schizocarp 1.4-1.6 by 1.6-1.9 mm, sulcate and hardly keeled. Seeds c. 1 by 0.6-0.7 mm, light brown to red-brown, neither papillate nor ridged (but completely smooth), ecarunculate.

    T h a i l a n d.— NORTH-EASTERN: Nong Khai, Sakon Nakhon; SOUTH-WESTERN: Kanchanaburi; CENTRAL: Phra Nakhon Si Ayutthaya (Bangsai); Nakhon Pathom (Mahidol University); Bangkok (Bangkhen, Chatuchak), Samut Prakan (Samut Prakan); SOUTH-EASTERN: Chachoengsao; Chon Buri (Koh Si Chang).

    D i s t r i b u t i on.— Widespread in the New World from the U.S.A. to South America (type from Venezuela), introduced in Africa (Kenia, Zimbabwe), India, Thailand, Taiwan, Malesia (Java, Philippines), and probably much further.

    E c o l o g y.— Weedy on roadsides, in lawns, gardens and often in flower pots (!), in heavily disturbed, open places but with not too much trampling, also on seasonally inundated sand bar at river; often on garden earth, tuff or limestone bedrock. Altitude: Sea level to c. 200 m. Flowering and fruiting: July-March (the whole year round?).

    V e r n a c u l a r.— Nam nom ratchasi lek (มร้์) (Central).

 

19. Euphorbia sessiliflora Roxb., Fl. Ind. ed. 1832, 3: 471. 1832; Boiss. in DC., Prodr. 15, 2: 76. 1862; Kurz, Forest Fl. Burma 2: 415. 1877; Hook.f., Fl. Brit. India 5: 257. 1887; Gagnep. in Lecomte, Fl. Indo-Chine 5: 242. 1925; P.H.Hô, Câyco Viêtnam 2, 1: 363, fig. 4677. 1992; Esser & Chayam., Harvard Papers Bot. 6: 265. 2001; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 285. 2005.— Euphorbia kerrii Craib, Bull. Misc. Inf. Kew 1911: 455. 1911; Contr. Fl. Siam: 181. 1912; Gagnep. in Lecomte, Fl. Indo-Chine 5: 255.1955; Radcl.-Sm., Kew Bull. 26: 265. 1972.— Tithymalus sessiliflorus (Roxb.) Klotzsch & Garcke, Abh. Königl. Akad. Wiss. Berlin 1859: 77. 1860.

 

Erect shrub, to 45 cm tall (to 1 m fide Gagnepain), unbranched, with thick, slightly succulent stem (to 5 mm diam.) and an irregularly shaped, woody tuber. Indumentum absent. Deciduous, often leafless when flowering. Leaves alternate, often absent in lower part; stipules irregularly scaly, c. 0.5 mm long, undivided; petioles absent or less than 5 mm long; blades elliptic to slightly obovate, c. 8-9 by 3-4.5 cm, slightly succulent, base narrowly acute, margin entire, apex rounded to subacute, slightly brighter below, midrib thick but additional venation very indistinct, not triplinerved, side veins in c. 8 pairs. Cyathia in lower part of stem, axillary, solitary or in groups of 3, reddish, with a short peduncle of 1-1.5 mm; central cyathium sessile, lateral cyathia on peduncle of c. 2 mm; involucral bracts in pairs, 2-4 mm long; glands 4-5, transversely elliptic, c. 0.3 by 1 mm, without appendages. Pistillate flowers pedicellate; short style column present, stigmas c. 1.5 mm long. Fruits: pedicel c. 4 mm long; immature schizocarp ovate-elliptic, 3 by 5 mm (mature fruits 6 by 8 mm fide Craib, loc. cit.). Seeds not studied, described by Craib (loc. cit.) as 3 mm in diam., subglobose, whitish, minutely pustulate.

    T h a i l a n d.— NORTHERN: Chiangmai (Tin Tok N. of Doi Chieng Dao), Lamphun/Chiangmai? (Lakhon, lectotype of E. kerrii: kerr 974, K, isolectotypes A, BM, TCD), Lampang (Palat); SOUTH-WESTERN: Kanchanaburi (Tung Yai Naresuan West).

    D i s t r i b u t i o n.— Burma (type), Thailand, Vietnam.

    E c o l o g y.— In open deciduous forest, bamboo forest, on rocky ground over limestone . Altitude: 300-640 m. Flowering: January, February, May.

    V e r n a c u l a r.— Chi doi duan (ีดด่) (Lampang); wan phra chim (่านพระิม) (Bangkok); khao kha (้า้า, ้า่า) (Central).

    U s e s.— Root used for poisoning fish.

    N o t e.— Despite the name, the species does not have sessile cyathia, as seen on Roxburgh’s type drawings in Kew and Calcutta. E. sessiliflora has been reported for Central Thailand (khao kha, wan phra chim), but this could not be verified.

 

20. Euphorbia thymifolia L., Sp. Pl.: 454. 1753; Roxb., Fl. Ind. ed. 1832, 3: 473. 1832; Miq., Fl. Ind. Bat. 1, 2: 420. 1859; Boiss. in DC., Prodr. 15, 2: 47. 1862; Hook.f., Fl. Brit. India 5: 252. 1887; Craib, Bull. Misc. Inf. Kew 1911: 456. 1911; Contr. Fl. Siam: 182. 1912; Ridl., Fl. Malay Penins. 3: 182. 1924; Gagnep. in Lecomte, Fl. Indo-Chine 5: 246. 1925; Burkill, Dict. Econ. Prod. Malay Pen. 1: 980. 1935; M.R.Hend., Malay. Wild Fl.: 461, fig.415 C. 1959; Backer & Bakh.f., Fl. Java 1: 503. 1964; Radcl.-Sm., Kew Bull. 26: 267. 1972; Whitmore, Tree Fl. Malaya 2: 96. 1973; P.H.Hô, Câyco Viêtnam 2, 1: 363, fig. 4679. 1992, p.p.; J.S.Ma, Fl. Reipubl. Pop. Sin. 44(3): 52, pl. 11 fig. 6-11. 1997; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 286, fig. 71. 2005.— Chamaesyce thymifolia (L.) Millsp., Publ. Field Mus. Nat. Hist Chicago, Bot. Ser. 2: 412. 1916.

 

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Perennial subshrub, forming dense mats up to 20 cm in diameter under trampling, otherwise partially erect and up to 10 cm tall, branched at base, with some smaller side branches above; greyish-green and usually reddish-purple tinged on all parts. Indumentum consisting of pale to creamish hairs, 0.2-0.7 mm long, curled to appressed when short (in particular on the fruits), loosely erect when longer, scattered but distinct on vegetative parts, on the stems often only above. Leaves opposite; interpetiolar stipules 0.7-1.2 mm long, completely free and linear, sometimes slightly split; petioles c. 0.5-1 mm long; blades broadly elliptic, the largest ones 4-7 by 3-5 mm, conspicuously smaller on side branches, base oblique with a cordate and an obtuse half, margin serrate, apex rounded, with scattered hairs above and below, distinctly brighter and hyalin-papillate below, triplinerved, additional side veins nearly invisible, c. 3-pairs. Cyathia grouped to few (c. 3) in axillary sessile clusters with several linear bracts, peduncle elongating to form small side branches few cm long with smaller leaves and apical cyathial clusters, distinctly pubescent. Involucre c. 0.7-0.8 mm long, split by maturing fruit; glands 4, c. 0.1 mm wide, stipitate, purple, with transversely elliptic, narrow, c. 0.2 mm wide, pinkish appendages; ovary sessile, pubescent, stigmas c. 0.5-0.6 mm long, mostly bifid. Fruits with a pedicel of 0.3-0.4 mm (shorter than the involucre) and therefore maturing in the cyathium; schizocarp 0.9-1.0 by 0.9-1.0 mm, sulcate and hardly carinate, distinctly short-appressed pubescent throughout. Seeds c. 0.8 by 0.4-0.5 mm, yellowish-brown, not papillate but with shallow, transverse furrows, ecarunculate.

    T h a i l a n d.— Certainly in all provinces, hitherto recorded for NORTHERN: Chiangmai, Nan, Lamphun, Uttaradit, Tak, Nakhon Sawan; NORTH-EASTERN: Nong Khai, Kalasin, Khon Khaen; EASTERN: Chaiyaphum, Ubon Ratchathani; SOUTH-WESTERN: Kanchanaburi, Prachuap Khiri Khan; CENTRAL: Chai Nat, Phra Nakhon Si Ayutthaya, Saraburi, Krung Thep, Samut Prakan; SOUTH-EASTERN: Chachoengsao, Chon Buri; PENINSULAR: Phuket, Nakon Si Thammarat, Phatthalung, Trang, Songkhla.

    D i s t r i b u t i o n.— Pantropical weed, origin and type locality uncertain.

    E c o l o g y.— Weedy in plantations of rubber, soybean or other crops, lawns and gardens, on open grassy places, roadsides, pavements and car parking areas, often on places with heavy trampling and one of the few species surviving in cracks of roads, but also on sand dunes in beach forests; on sand or earth, limestone or granite bedrock. Altitude: sea level to 800 m (outside of Thailand known from c. 2,000 m). Flowering and fruiting: the whole year through.

    V e r n a c u l a r.— Nam nom ratchasi lek (มร้์) (Central); no chi yong () (Karen-Kanchanaburi).

    U s e s.— In Arabia and Java the leaves are applied to skin complaints and wounds. Dried leaves and seeds are adstringent and used in India and Java against diarrhoea and dysentery by children.

 

21. Euphorbia sp.: Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 288. 2005.

 

Succulent, usually leafless shrub to 2 m tall; oldest parts unknown, branches distinctly 4-5-angled, with distinct wings, articulate with the segments 11 by 1.5 cm, without sinuses between the spine-shields. Spine-shields in rows, 10-15 mm apart; spines in pairs, blackish-brown, 4-5 mm long, partly deciduous. Indumentum absent. Stipules transformed into spines. Leaves very soon caducous, not seen. Cyathia axillary, in dichasia of 3; basal peduncle 2 mm long; bracts of branching c. 2 mm long; peduncle of fruiting cyathia 4 mm long; flowering cyathia unknown. Fruits with a pedicel of 2 mm, but not extending beyond the cyathium (appearing subsessile); schizocarp 3 by 4 mm, hardly sulcate. Seeds unknown.

    T h a i l a n d.— PENINSULAR: Trang (Bangsak).

    D i s t r i bu t i o n.— Only known from Thailand.

    E c o l o g y.— In rocky limestone hill. Altitude: sea level. Flowering: February; fruiting: February, April.

    V e r n a c u l a r.— Salat dai (ลัดได).

    N o t e.— One collection (Kerr 19048) differs from E. antiquorum in the higher number of wings, very narrow branches, mostly deciduous spines and in the remarkably small, nearly sessile fruits. In the general habit it approaches E. royleana Boiss., an Himalayan species not known from Thailand. E. royleana, however, has much shorter (1-2 mm long), pale brown spines, and larger, deeply sulcate fruits (c. 3 by 10 mm). Another collection from Chaiyaphum province (Phu Wieng: Kerr 20165) appears intermediate with Kerr 19048 and typical E. antiquorum, having fruits like the latter, but narrow, 5-angled branches with narrow sinuses between spine-shields and persistent spines. The status of these collections cannot be decided at this moment. If Kerr 19048 does not represent an aberrant collection of E. antiquorum, it would be an undescribed species.

 

Cultivated species

 

22. Euphorbia cotinifolia L. subsp. cotinoides (Miq.) Christenhusz, Harvard Papers Bot. 7: 3. 2002; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 288. 2005.— Euphorbia cotinoides Miq., Linnaea 21: 473. 1848; Boiss. in DC., Prodr. 15, 2: 60. 1862; Binojkumar & N.P.Balakr., J. Econ. Tax. Bot. 15: 463. 1991.— Euphorbia cotinifolia auct. non L.: J.S.Ma, Fl. Reipubl. Pop. Sin. 44(3): 57, pl. 13 fig. 5-7. 1997.

 

Shrub to 2 m tall, neither succulent nor spiny, most parts often pinkish to reddish-purple; terminal branches in whorls. Indumentum very short, only on cyathia. Stipules c. 0.3 mm long, soon caducous. Leaves in whorls of 3 (rarely opposite); petiole 3-6 cm long, nearly as long as the blade; blade ovate, 4-6 by 3-4 cm, base obtuse-rounded, margin entire, apex acute (rarely obtuse), venation distinct. Cyathia yellow-cream, in terminal and axillary, elongate dichasia, the bracts linear-triangular, c. 2 mm long; cyathial glands 4, c. 0.7 by 1 mm; their appendages c. 1 by 2 mm, whitish. Fruits c. 4 mm in diam., sparsely hairy to glabrous. Seeds c. 2.5 by 2 mm, brown, foveolate, ecarunculate.

    D i s t r i b u t i o n.— Typical E. cotinifolia (from the Antilles and Venezuela, type from Curaçao) differs in orbiculate, apically rounded leaves and some additional characters. Only the ovate-leaved form, described as E. cotinoides (type from Surinam), and originally South-American, is found cultivated throughout the tropics.

    V e r n a c u l a r.— Pho daeng yai (ดงใญ่) (Central).

    U s e s.— Ornamental shrub, the leaves being reddish-purple. The latex of this species is very toxic and blisters the skin. In the Neotropics therefore used as a fish poison.

 

23. Euphorbia lactea Haw., Syn. Pl. Succ.: 127. 1812; Roxb., Fl. Ind. ed. 1832, 3: 468. 1832; Miq., Fl. Ind. Bat. 1, 2: 418. 1859; Boiss. in DC., Prodr. 15, 2: 82. 1862; Croizat, Euphorb. Antiq.: 52. 1934; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 289. 2005.

 

Succulent, spiny shrub to 2 m tall, basal diam. to c. 20 cm, erect, branched from immediately above the base; older parts terete, younger branches distinctly 3(-4)-angled, ascending, bark green, whitish marbled or whitish-greyish throughout; youngest branches c. 3-17 by 1.5-3 cm, slightly constricted and often biplanar at their base, sinuses between spine-shields c. 5 mm deep. Spine-shields c. 10-15 mm apart, spines in pairs, 2-3 mm long, blackish to brown, persistent. Indumentum absent. Leaves alternate, rarely present, scale-like, c. 4 by 3 mm, orbicular. Neither flowering nor fruiting.

    D i s t r i b u t i o n.— Widely cultivated, origin unknown (type from ‘India orientalis’).

    V e r n a c u l a r.— Salatdai lueang (ลัดไดลื) (Central).

    U s e s.— Widely cultivated as cactus-like garden ornamental, although never flowering. Branch segments root very easily.

 

24. Euphorbia leucocephala Lotsy, Coult. Bot. Gaz. 20: 350, tab. 24. 1895; Binojkumar & N.P.Balakr., Indian J. Forestry 15: 181. 1992; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 289. 2005.

 

Shrub to 2 m tall, neither succulent nor spiny, densely branching. Indumentum present, pale brownish. Stipules small (c. 0.3 mm), triangular. Leaves opposite; petiole 7-20 mm long; blade elliptic, 2.2-2.5 by 0.5-0.7 cm, acutish at both ends, entire, venation distinct. Cyathia in large dichasia, their bracts white and showy, c. 7 by 2 mm; cyathial glands 5, c. 0.3 by 1 mm, with petal-like appendages c. 2 by 1 mm. Fruits subsessile (pedicel c.1 mm); schizocarp c. 7 by 5 mm, hardly sulcate, glabrous. Seeds 4 by 2.5 mm, greyish, tuberculate, ecarunculate.

    D i s t r i b u t i o n.— Originally from Central America (type from Guatemala), widely cultivated elsewhere.

    V e r n a c u l a r .— Khritmat khao (ริสิส), khritmat nu (ริสิสหนู), salatdai pradap khao (ลัดไดระดับข) (Central).

    U s e s.— Ornamental shrub, with conspicuous large white bracts.

 

25. Euphorbia milii Des Moul., Bull. Hist. Nat. Soc. Linn. Bordeaux 1: 27, pl. 1. 1826; Croizat, J. Arnold Arbor. 21: 506. 1940; Radcl.-Sm., Kew Bull. 26: 266. 1972; P.H.Hô, Câyco Viêtnam 2, 1: 359, fig. 4665. 1992; J.S.Ma, Fl. Reipubl. Pop. Sin. 44(3): 58, pl. 14 fig. 1-4. 1997; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 290. 2005. Euphorbia splendens Bojer ex Hook., Bot. Mag. 56: t. 2902. 1829; Boiss. in DC., Prodr. 15, 2: 79. 1862; Gagnep. in Lecomte, Fl. Indo-Chine 5: 239. 1925.

 

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Erect shrub, succulent, spiny, stem terete, bark brown to grayish; younger branches c. 8 mm in diam. Spines in spirals or indistinct rows, not on spineshields, solitary or in groups of 3 or more, 16-25 mm long, grey to brown. Indumentum absent. Leaves alternate or in indistinct rows, subsessile; blade obovate-elliptic, c. 1.5-5 by 0.8-2 cm, base attenuate to rounded, margin entire, apex obtuse to acute or mucronate, venation hardly visible. Cyathia several in exserted dichasia with long peduncles; bracts at branching 2 mm long, membranous, inconspicuous; bracts below cyathia in pairs, red or yellow or white or in various colours, showy and petaloid, 1-2 cm long; cyathia sessile in bracts, glands 4, without appendages. Fruits and seeds not seen, the seeds described as 3-4 mm long, brownish.

    D i s t r i b u t i o n.— Origin Madagascar, widely cultivated elsewhere.

    U s e s.— Widespread ornamental shrub in gardens and houses, in the temperate zones as indoor plant. In Thailand widely grown and bred in numerous forms and varieties, and considered as good luck plants. It flowers nearly continuously.

    V e r n a c u l a r.— Wan mung mueang (่าน) (Mae Hong Son); phra chao rop lok (ระ้าูล), poi sian (ซี), rawing rawai (ระระ), wan khem phaya in (่านข็พญาอิร์) (Chiang Mai); mai rap khaek (บแข) (Central); Christ Thorn, Crown of Thorns (English).

    N o t e.— The typical Crowns of Thorns bred in Thailand are a hybrid between E. milii and a related species from Madagascar, and are correctly called Euphorbia x lomi Rauh, Kakteen Sukk. 30: 257. 1979 (E. milii Des Moul. X E. lophogona Lam.). They are distinguished from E. milii by the spines in groups of irregular number and considerably larger cyathial bracts. The horticultural taxonomy was discussed by Jankalski, Cact. Succ. J. (USA) 72: 202-204. 2000.

 

26. Euphorbia neriifolia L., Sp. Pl.: 451. 1753; Lour., Fl. Cochinch.: 298. 1790; Boiss. in DC., Prodr. 15, 2: 79. 1862; Kurz, Forest Fl. Burma 2: 416. 1877; Hook.f., Fl. Brit. India 5: 255. 1887; Ridl., Fl. Malay Penins. 3: 182. 1924; Gagnep. in Lecomte, Fl. Indo-Chine 5: 239. 1925; Merr., Trans. Amer. Philos. Soc. n.s. 24: 242. 1935; Burkill, Dict. Econ. Prod. Malay Pen. 1: 979. 1935; Wijnands, Bot. Commel.: 100. 1983; Corner, Wayside Trees Mal. ed. 3, 1: 291. 1988; J.S.Ma, Fl. Reipubl. Pop. Sin. 44(3): 60, pl. 15 fig. 1-3. 1997; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 290. 2005.— Ligularia Rumph., Herb. Amb. 4: 88, t. 11. 1743, nom. inval.— Euphorbia ligularia Roxb., (Hort. Bengal.: 36. 1814, nomen) ex Buch.-Ham., Trans. Linn. Soc. 14: 285. 1825, nom. illeg.; Roxb, Fl. Ind. ed. 1832: 465. 1832; Miq., Fl. Ind. Bat. 1, 2: 418. 1859; Boiss. in DC., Prodr. 15, 2: 79. 1862 (as syn. nov.); Backer & Bakh.f., Fl. Java 1: 501. 1964; Radcl.-Sm., Kew Bull. 26: 265. 1972; P.H.Hô, Câyco Viêtnam 2, 1: 358, fig. 4663. 1992.— Euphorbia edulis Lour., Fl. Cochinch.: 298. 1790; Boiss. in DC., Prodr. 15, 2: 80. 1862; Gagnep. in Lecomte, Fl. Indo-Chine 5: 254. 1925 (as probable var.); Merr., Trans. Amer. Philos. Soc. n.s. 24: 242. 1935 (as syn. nov.).

 

Erect shrub, to 4 m tall, fleshy and slightly succulent, base diam. to 6 cm, spiny, branching, usually with terminal leaves; stem and branches without articulation, base nearly terete, otherwise with 5 indistinct angles (not winged) and spine-shields in 5 distinct rows, younger branches c. 15 mm in diam., sinuses between spine-shields shallow to absent. Spine-shields 2-3 cm apart, spines in pairs, 2 mm long, grey-brown to blackish, persistent. Indumentum absent. Stipules transformed into spines. Leaves subsessile, obovate, 10-18 by 3-4 cm, base attenuate, margin entire, apex rounded, persistent during the vegetation period. Cyathia not seen in Thailand, outside of Thailand arranged in axillary groups of 3, the central one subsessile, the lateral ones with a peduncle of 6-7 mm, bracts 4 mm long, cyathial glands 5, 1 by 3 mm. Flowers and fruits not seen.

    D i s t r i b u t i o n.— Dry tropics of S. India, but widely cultivated in tropical Asia (type from the Moluccas) as hedge plant and garden ornamental.

    V e r n a c u l a r.— Som chao (้า) (Central).

    U s e s.— Latex used to remove warts. The root mixed with black pepper is applied to cure snake bites (Roxburgh, loc. cit.). Leaves after extraction of latex by punctures preserved in syrup as sweetmeat (Ridley, loc. cit.). Loureiro (under E. edulis) noted the leaves are, together with other pot herbs, eaten. The juice of heated leaves is dropped into ears for ear-ache in Malacca (Burkill, loc. cit.). The latex is purgative. Fish-poison.

 

27. Euphorbia tirucalli L., Sp. Pl.: 452. 1753; Lour., Fl. Cochinch.: 299. 1790; Roxb., Fl. Ind. ed. 1832, 3: 470. 1832; Miq., Fl. Ind. Bat. 1, 2: 420. 1859; Boiss. in DC., Prodr. 15, 2: 96. 1862; Hook.f., Fl. Brit. India 5: 254. 1887; Ridl., Fl. Malay Penins. 3: 182. 1924; Gagnep. in Lecomte, Fl. Indo-Chine 5: 254. 1925; Radcl-Sm., Kew Bull. 26: 267. 1972; Leach, Kirkia 9: 69. 1973; Corner, Wayside Trees Mal. ed. 3, 1: 291. 1988; P.H.Hô, Câyco Viêtnam 2, 1: 356, fig. 4658. 1992; J.S.Ma, Fl. Reipubl. Pop. Sin. 44(3): 58, pl. 14 fig. 5. 1997; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 291. 2005.— Arthrothamnus tirucalli (L.) Klotzsch & Garcke, Abh. Königl. Akad. Wiss. Berlin 1859: 62. 1860.

 

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Shrub to 2.5 m tall, monoecious or staminate only, succulent and woody, without spines, usually leafless, with dichotomous or whorled branching; branches elongate, only 3-6 mm in diam., slightly tomentose at apex. Indumentum present, pale. Stipules very small (c. 0.3 mm), glandular. Leaves alternate, obovate-linear, 10 by 1-1.5 mm, very soon caducous. Cyathia green, in subsessile, capitate glomerules, tomentose to glabrous, many-flowered glomerules often with staminate flowers only; cyathial glands 4, c. 0.5 by 1-1.5 mm, without appendages. Pistillate flowers tomentose, with a distinct perianth. Fruits exserted, c. 7 mm long, glabrescent. Seeds brown and often mottled, 4 by 3 mm, smooth, carunculate.

    D i s t r i b u t i o n.— Africa from Ethiopia to S. Africa (probable origin: Angola), widely cultivated in Madagascar and Asia (type from Sri Lanka).

    U s e s.— Medicinal plant (purgative). In Africa often used as a living fence because branch cuttings root very easily. The latex however is very toxic, therefore in Africa used as fish poison.

    V e r n a c u l a r.— Khia chin (เีน), phaya rai bai (พญาไ้ใ), phaya roi bai (พญา) (Chiang Mai); khia thian (เ) (Northern).

 

28. Euphorbia trigona Mill., Gard. Dict. Ed. 8: Euphorbia number 3. 1768; Haw., Syn. Pl. Succ.: 127. 1812; Croizat, Euphorb. Antiq.: 39. 1934; Wijnands, Bot. Commelins: 102. 1982; Koutnik, Euphorbia J. 7: 11. 1991; P.H.Hô, Câyco Viêtnam 2, 1: 358, fig. 4664. 1992; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 291. 2005.— Euphorbia hermentiana Lem., L’Illustr. Hort. 5: 63. 1858; Boiss. in DC., Prodr. 15, 2: 82. 1862.

 

Succulent, spiny shrub to 3 m tall, basal diam. up to to c. 10 cm, erect, branched from above the base; older parts terete or 4-angled, younger branches distinctly 3-angled, ascending and appressed to the stem; youngest branches elongate, c. 2-3 cm in diam., not constricted at their base, bark green or whitish marbled, sinuses between spine-shields c. 5 mm deep. Spine-shields c. 10 mm apart, spines in pairs, c. 4 mm long, grey-brown, persistent. Indumentum absent. Stipules transformed into spines. Leaves obovate-elliptic, c. 10-30 by 5-10 mm, deciduous but persistent for some time and therefore often present. Neither flowering nor fruiting.

    D i s t r i b u t i o n.— Widely cultivated, but probable origin in Africa (type of unknown origin).

    V e r n a c u l a r.— Khia ua (เั้) (Mae Hong Son); salat dai ban (ลัดได้าน) (Central).

    U s e s.— Ornamental plant, often potted.

    N o t e.---The name of E. trigona has often been misapplied. Because it never flowers, its wild relatives are still uncertain.