Flora of Thailand

Euphorbiaceae

 

30. Croton

 

H.-J. Esser

 

This treatment differs from Flora of Thailand: Croton fluviatilis is newly described and replaces C. sp. 2

 

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Genus description

Identification key

Species descriptions

Excluded names

 

Croton

 

L., Sp. Pl.: 1004. 1753; Mll.Arg. in DC., Prodr. 15, 2: 512. 1866; Benth. in Benth. & Hook.f., Gen. Pl. 3: 293. 1880; Hook.f., Fl. Brit. India 5: 385. 1887; Gagnep. in Lecomte, Fl. Indo-Chine 5: 256. 1925; Pax & K.Hoffm. in Engl. & Harms, Nat. Pflanzenfam. ed. 2, 19c: 83. 1931; Airy Shaw, Kew Bull. 26: 241. 1972; G.L.Webster, Taxon 42: 793. 1993; Ann. Missouri Bot. Gard. 81: 111. 1994; Radcl.-Sm., Gen. Euphorbiacearum: 319. 2001; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 189. 2005; G.L.Webster in Kubitzki, Fam. Gen. Vasc. Pl. 11: 169, Fig. 39. 2014. Tridesmis Lour., Fl. Cochinch.: 576. 1790. Tiglium Klotzsch, Nov. Act. Acad. Caes. Leop.-Carol. Nat. Cur. 19 (suppl.) 1: 418. 1843.

 

Trees, shrubs or herbs, sometimes climbing, monoecious; branching usually verticillate; latex colourless or red. Indumentum consisting of stellate to lepidote, variously coloured hairs. Stipules linear to triangular, eglandular or with marginal glandular lobes, caducous. Leaves alternate to crowded, sometimes pseudo-verticillate; petiole distinct, eglandular, rarely glandular; blade simple, symmetric, variable in shape and margin, pubescent to a various degree, always with a pair of glands on the upper or lower base of blade or midrib or on the petiole apex, sometimes with additional marginal glands; venation usually visible on both surfaces, pinnate or palmate (triplinerved), side veins arching and hardly to distinctly looped (but always distinctly looped at the apex), tertiary veinlets percurrent to more often reticulate. Inflorescences terminal or subterminal, unbranched, elongate thyrses, bisexual, a basal part pistillate with 1 flower per bract, the apical part staminate with 1-3(-5) flowers per bract, more rarely completely pistillate or staminate, the pistillate flowers sometimes with lateral staminate flowers (with bisexual bracts); pubescent at least in parts; bracts triangular-ovate, glandular or eglandular, persistent or caducous. Flowers actinomorphic, pedicellate; sepals 5, ovate-elliptic, fused at base; petals 5, free. Staminate flowers: petals similar to sepals but less pubescent and with a ciliate-lanate margin; disc lobed, receptacle pilose (the flowers therefore filled with whitish hairs c. 1 mm long); stamens 10-20, inflexed in bud, free, filaments longer than the anthers, anthers 2-locular, basifixed; pistillode absent. Pistillate flowers pubescent at least in parts; petals much smaller than the sepals or more often absent; staminodes absent; ovary 3-locular, smooth or muriculate, always pubescent (in Thailand), with 1 ovule per carpel; style column short or absent, stigmas 3, bifid to a various degree, sometimes even quadrifid. Fruits 3-locular, small to large, nearly globose, usually sulcate, smooth or shallowly muriculate, pubescent (in Thailand), dry and dehiscent. Seeds 3 per fruit, dry, ellipsoid, brown, glabrous or (rarely) with scattered hairs, smooth, with or without a caruncle.

    Eight-hundred or more species, pantropical with the center of diversity (species and sections) in America; in Asia slightly less than 100 species, 30 species in Thailand. Classification: Subfamily Crotonoideae, tribe Crotoneae.

    N o t e.  Natural subdivisions of this vast genus are still not well understood, in particular not in Asia.

 

Key to the species

 

1a.

Herbs or weedy subshrubs, up to 1 m tall.

2

1b.

Climbers, shrubs or trees, with distinctly woody stem, 0.5-30 m tall.

3

2a.

Indumentum of small (0.3-0.5 mm wide), flat, not irritating hairs, visible as whitish dots. Leaves 1-2 cm wide, distinctly longer than wide (index 1.5-3.5), with dense, simple serration. Basal leaf glands prominent but sessile. Floral bracts to 1 mm long, simple.

3. C. bonplandianus

2b.

Indumentum of large (0.5-2 mm wide), hispid, irritating hairs. Leaves 2-4 cm wide, hardly longer than wide (index 1.0-1.6), with coarse double-serration. Basal leaf glands distinctly stalked. Floral bracts 1-2 mm long, glandular-ciliate.

12. C. hirtus

3a.

Young and mature leaves completely and densely pubescent below, appearing silvery-whitish to golden or brownish, surface not visible between the hairs.

4

3b.

Mature leaves with dense to scattered hairs below or glabrous, not completely silvery-whitish or golden-brown, the surface visible between the hairs.

12

4a.

Leaves serrate to subentire, above with stellate, brownish hairs and distinct venation (venation impressed to raised in dried leaves). Basal leaf glands stalked, additional marginal glands often present.

5

4b.

Leaves entire, above glabrous or with lepidote, mostly whitish-hyaline hairs and invisible or raised venation. Basal leaf glands flat and sessile, additional marginal glands absent.

6

5a.

Crooked, erect shrub, hardly branched. Leaves with coarse double-serration to subentire, above with hispid-dendritic hairs. Stipules and floral bracts often persistent, glandular-ciliate with black-capitate glands, conspicuous.

7. C. crassifolius

5b.

Straggling shrub with rich branching. Leaves with dense, simple serration, above with flat hairs. Stipules entire and eglandular, inconspicuous and caducous; floral bracts soon caducous, not seen.

17. C. krabas

6a.

Leaves (elliptic to) ovate, slowly glabrescent above, very distinctly triplinerved with the basal side veins originating from the base of the blade. Glands of leaf base abaxial-laterally on petiole apex, often visible from above. Fruits c. 5 mm long.

15. C. kongensis

6b.

Leaves variously shaped, very soon glabrescent above, not triplinerved or, if triplinerved, with the basal veins originating from above the base of the blade. Glands of leaf base on abaxial base of midrib or absent, not visible from above. Fruits 4-27 mm long.

7

7a.

Venation of the lower leaf surface covered by hyaline hairs, not differing in colour in dried leaves, veinlets nearly invisible. Inflorescences 0.5-6 cm long. Fruits 4-5 mm long.

8

7b.

At least larger veins of the lower leaf surface covered by brownish hairs, of different colour in dried leaves, veinlets visible. Inflorescences (1.5-)3-20 cm long. Fruits 7-27 mm long.

9

8a.

Leaves 3.5-7 cm wide, often (but not always) pseudo-verticillate, the apex acuminate. Hairs on lower leaf surface large (0.5-1 mm in diam.), scattered darker ones visible as distinct dots. Inflorescences 0.5-2 cm long. Stigmas shed in fruit.

4. C. cascarilloides

8b.

Leaves 1-2.5 cm wide, a few pseudo-verticillate apically but mostly alternate, the apex rounded to subacuminate. Hairs on lower leaf surface small (0.2-0.4 mm in diam.), of homogeneous colour. Inflorescences 2-6 cm long. Stigmas persistent in fruit.

20. C. mekongensis

9a.

Mature leaves silvery with small reddish-brown dots on the whole surface below, not purely silvery, base acute to obtuse with only the very base slightly cordulate, index 2.1-4.0; venation not to slightly triplinerved. Inflorescences (1.5-)3-13(-20) cm long.

10

9b.

Mature leaves purely silvery below with no reddish-brownish dots below except on largest veins, base obtuse to distinctly cordate, index 1.5-2.3; venation not triplinerved. Inflorescences 8-25 cm long.

11

10a.

  Leaves ovate, 15-28 cm long, with 13-16 pairs of side veins below the apex. Inflorescences 3-13(-20) cm long. Fruits 15-17 mm long.

23. C. poomae

10b.

Leaves elliptic to very slightly ovate or obovate, 8-21 cm long, with 6-8(-11) pairs of side veins below the apex. Inflorescences 1.5-5.5 cm long. Fruits 7 mm long.

26. C. sepalinus

11a.

Fruits 12-16 mm long. Peninsular Thailand.

2. C. argyratus

11b.

Fruits 22-27 mm long. Northern to South-Eastern.

16. C. kongkandanus

12a.

Leaves distinctly triplinerved.

13

12b.

Leaves not or very indistinctly triplinerved.

16

13a.

Leaves glabrous to pubescent, their basal glands on the basal blade margin, sessile to stalked. Fruits 13-20 mm long, very thin-walled and fragile.

29. C. tiglium

13b.

Leaves distinctly pubescent, their basal glands on the midrib base, stalked. Fruits less than 10 mm long or, if larger, very thick-walled.

14

14a.

Plant a woody climber. Fruits 12-18 mm long. Floral bracts 2-5 mm long, entire.

5. C. caudatus

14b.

Plant an erect shrub. Fruits less than 10 mm long. Floral bracts smaller (1-1.5 mm long) or with glandular lobes.

15

15a.

Crooked, thickly woody shrub to 1 m tall. Leaves chartaceous to coriaceous, with dense, regularly hispid hairs. Floral bracts 2-4 mm long, with glandular lobes. Fruits with a short pedicel (1-2 mm long) and partly fused sepals.

7. C. crassifolius

15b.

Thin shrub to 3 m tall. Leaves membranous, with scattered hairs, these on leaves often reduced to a single hispid radius. Floral bracts 1-1.5 mm long, entire. Fruits with a distinct pedicel (3-8 mm long) and free sepals.

18. C. lachnocarpus

16a.

Leaf blades obovate(-elliptic) and sometimes constricted near base, petiole and abaxial blade usually slightly but not densely pubescent. Basal leaf glands partly or completely on the abaxial blade surface, only touching the midrib, and often elongate-narrowed. Inflorescences distinctly proterogynous, often even with precocious fruits (staminate buds together with fruits).

17

16b.

Leaf blades variously shaped, but rarely distinctly obovate and then glabrous and not constricted near base, glabrous to distinctly pubescent. Basal leaf glands on the midrib base or petiole apex, regularly rounded to elongate. Inflorescences unisexual or slightly proterogynous only (rarely precocious fruits: C. columnaris). 

19

17a.

Inflorescence buds stiff, erect, sometimes on a bent stalk, occuring in plants with leaves. Central to South-Eastern, cultivated elsewhere.

27. C. stellatopilosus

17b.

Inflorescence buds inconspicuous, weak, not on a bent stalk. Peninsular to Northern.

18

18a.

Leaf blades narrowly obovate-elliptic (index 2.7-6.1), 3-4 cm wide. Plants flowering when with mature leaves. Only known cultivated in Northern.

19. C. longissimus

18b.

Leaf blades obovate-elliptic (index 2.0-3.3), 5-10 cm wide. Plants often flowering when leafless or with young leaves. Peninsular to South-Western.

30. C. wallichii

19a.

Basal leaf glands stalked, longer than wide.

20

19b.

Basal leaf glands sessile (flat to prominent, wider than long).

21

20a.

Leaves (sub-)glabrous, never ovate, their base obtuse.

14. C. kerrii

20b.

Leaves distinctly pubescent on both sides, often ovate, their base rounded to cordate.

18. C. lachnocarpus

21a.

Leaf blades slowly glabrescent, mature ones distinctly pubescent on the whole surface below, margin very indistinctly serrate to subentire. Bark corky, with deep furrows. Sap turning red.

13. C. hutchinsonianus

21b.

Leaf blades soon glabrescent, mature ones with scattered hairs only (often on midrib) or glabrous below (the petiole however often densely pubescent), margin distinctly serrate to entire. Bark not corky, without deep furrows (but undescribed in some species). Sap not turning red.

22

22a.

Hairs (at least on vegetative parts) lepidote with c. 25-45 fused radii.

23

22b.

Hairs always stellate with c. 10-30 not to partly fused radii.

27

23a.

Rheophytic shrub with linear leaves (index (5-)7.5-10.5).

10. C. fluviatilis

23b.

Non-rheophytic shrub to tree, leaves elliptic (index 2.0-4.2).

24

24a.

Basal leaf glands adaxial-lateral on petiole apex, only visible from above.

21. C. phuquocensis

24b.

Basal leaf glands abaxial-lateral on midrib base, only visible from below.

25

25a.

Hairs creamish-yellowish. Leaves (sub-)entire. All floral parts densely and persistently pubescent. Floral pedicels 1(-2) mm long.

24. C. robustus

25b.

Hairs pale-grey-brown to hyaline. Leaves distinctly serrate. Some floral parts glabrescent. Floral pedicels (1-)2-5 mm long. 

26

26a.

Leaves with teeth (5-)7-13 mm apart. Inflorescence axis persistently pubescent. Sepals of pistillate flowers 5-7 mm long, distinctly longer than the ovary and glabrous in upper part. Fruits 11 mm long.

22. C. poilanei

26b.

Leaves with teeth only 3-5(-7) mm apart. Inflorescence axis glabrescent. Sepals of pistillate flowers 2.5-3 mm long, not to slightly longer than the ovary and completely pubescent. Fruits 6-7 mm long. 

25. C. roxburghii

27a.

Petioles long (2.5-12 cm), with few hairs to glabrous. Leaves drying yellowish-brown, apically rounded to mucronate (rarely subacuminate). Inflorescences nearly glabrous (only the ovary distinctly pubescent).

11. C. griffithii

27b.

 Petioles short to long (0.3-7 cm), distinctly pubescent. Leaves drying yellowish-brown or not, apically acute to acuminate (if rounded then inflorescences densely pubescent). Inflorescences distinctly pubescent. 

28

28a.

Leaves (sub-)entire, apex acute. Inflorescences mostly with staminate flowers only, usually several in an apical pseudo-whorl. Pedicels of staminate flowers 3-5 mm long. Pistillate flowers and fruits rare, their pedicels 8-13 mm long.

1. C. acutifolius

28b.

Leaves subentire to distinctly serrate, apex rounded to acute to acuminate. Inflorescences usually with both sexes, solitary or several per apex. Pedicels of staminate flowers 1-3 mm long. Pedicels of pistillate flowers and fruits 0.5-7 mm long.

29

29a.

Leaves distinctly serrate, elliptic to rhomboid, their basal glands usually on the petiole apex. Styles united into a short column 1-2 mm long.

6. C. columnaris

29b.

Leaves entire to serrate, elliptic to oblong, their basal glands on the midrib base. Styles free, not united into a column.

30

30a.

Inflorescences densely and persistently pubescent on all parts (only bracts sometimes glabrescent).

31

30b.

Inflorescences persistently pubescent or glabrescent on the axis, but at least the sepals soon glabrescent.

33

31a.

Leaves often pseudo-verticillate, petioles 0.3-0.9 cm long.

28. C. thorelii

31b.

Leaves pseudo-verticillate to alternate, petioles (0.4-)1.2-7 cm long.

32

32a.

Hairs yellowish-cream, with an undivided darker center. Leaves indistinctly serrate. Pedicels of flowers 1(-2) mm long.

24. C. robustus

32b.

Hairs pale creamish-grey, without a darker center, radii free. Leaves distinctly serrate. Pedicels of flowers 2-5 mm long.

31. Croton sp. 1

33a.

Leaves pseudo-verticillate at nodes, alternate between, petiole 0.4-1.6 cm long. Inflorescences glabrescent on most parts incl. the axis, only the pedicels often not glabrescent. Floral bracts 3-5 mm long, usually soon caducous.

8. C. decalvatus

33b.

Leaves alternate to crowded but not pseudo-verticillate, petiole 0.8-7 cm long. Inflorescences densely and persistently pubescent on most parts incl. the axis, only the sepals and bracts glabrescent. Floral bracts 2-3 mm long, quite persistent.

9. C. delpyi

         

1. Croton acutifolius Esser, Thai For. Bull. (Bot.) 29: 51. 2001; in Chayam. & Welzen, Fl. Thailand 8, 1: 193, fig. 44. 2005. Croton robustus auct. non Kurz: Craib, Bull. Misc. Inform. Kew 1911: 464. 1911; Contr. Fl. Siam: 190. 1912; Gagnep. in Lecomte, Fl. Indo-Chine 5: 289. 1925; Airy Shaw, Kew Bull. 26: 249. 1972, p.p. excl. C. siamensis. Croton oblongifolius auct. non Roxb.: Hosseus, Beih. Bot. Centralbl. 28: 404. 1911.

 

 

Shrub or tree to 12 m, dbh up to 25 cm; bark thick, scaly and roughly vertically cracked, grey-brownish; branchlets slowly glabrescent. Indumentum consisting of stellate, flat to dendritic, yellowish-brown hairs with pale radii (appear creamy-yellowish), 0.2-0.3 mm (on flowers up to 0.5 mm) in diam., with c. 20-25 free radii. Stipules 1-1.5 mm long, densely pubescent. Leaves alternate, often crowded; petiole 1.0-2.5 cm long, densely pubescent, hardly glabrescent; blade elliptic, 12-22 by 4-9.5 cm, index 2.8-3.8, chartaceous, base acute, margin subentire with very shallow and indistinct serration, apex acute, slightly brighter below, glabrous above, below densely pubescent at the very base and sparsely pubescent on the midrib, otherwise subglabrous with few scattered hairs; basal glands flat, sessile, c. 0.5 mm in diam., lateral on the abaxial midrib base, marginal glands absent; side veins 15-20 pairs, not triplinerved. Inflorescences whitish-green to greyish-green, quite often several in an apical leafless whorl or with immature leaves, each one 8-24 cm long, most often completely staminate, rarely with 3-8 pistillate flowers, sometimes with bisexual bracts; densely and persistently pubescent throughout; bracts 1.5-2 mm long, stiff, persistent, eglandular. Staminate flowers densely pubescent; pedicel 3-5 mm long; sepals 2 by 1 mm; petals 2 by 1 mm, stellate-pubescent outside; stamens c. 10, with filaments often pubescent. Pistillate flowers densely pubescent; pedicel 8-10 mm long (10-13 mm in fruit); sepals 2-3 by 1-1.5 mm, slightly shorter than the ovary, pubescent throughout outside; petals absent or as c. 1 by 0.2 mm, lineal lobes; ovary c. 3 mm long; stigmas 3-4 mm long, not fused at base, undivided for c. 1 mm at base and divided apically. Fruits 6-7 by 8-9 mm, sulcate, densely pubescent and smooth outside. Seeds 6 by 4 mm, with a rudimentary caruncle.

    T h a i l a n d.  NORTHERN: Mae Hong Son (Tham Nam Lot), Chiang Mai (Doi Chiang Dao, Doi Inthanon, Doi Sang, Doi Suthep, Mae Taeng, Mae Rim), Chiang Rai (Doi Luang, Khun Chae, Mae Fa Luang, Mae Suai), Nan (Doi Phu Kha), Lampang (Doi Khuntan, Chae Son, type: Maxwell 96-4, holotype BKF, isotypes A, CAS n.v., CMU, L), Phitsanulok (Phu Miang-Phu Thong); NORTH-EASTERN: Phetchabun (Nam Nao).

    D i s t r i b u t i o n. Endemic? To be expected in Laos.

    E c o l o g y. In disturbed hill evergreen, evergreen or deciduous seasonal hardwood, hardwood and pine, or mixed evergreen/deciduous forest, secondary thickets, clearings and fire-prone places; on lateritic or clayey soil, over granite or limestone. Altitude: (400-)600-1,400 m. Flowering: October-March (August); fruiting: January-April (August). Inflorescences fragrant.

    V e r n a c u l a r. Chi-mi-chi-ya (จิมิจิยา; Akha-Chiang Rai); mado kai (มะดอไก่) (Red Lahu-Chiang Mai); plao (เปล้า), plao phae (เปล้าแพะ) (Northern).

    U s e s. The leaves, in mixture with other plants, are used for cuts.

    N o t e. The species is superficially similar to C. robustus, with which it was confused. Both taxa do not overlap in their range, and differ in hair morphology, leaf shape, pedicels of flowers and fruits, distribution of sexes, ecology and distribution.

 

2. Croton argyratus Blume, Bijdr: 602. 1826; Miq., Fl. Ind. Bat. 1, 2: 380. 1859; Mll.Arg. in DC., Prodr. 15, 2: 526. 1866; Ridl., Fl. Malay Pen. 3: 260. 1924, p.p. excl. C. adumbratus; Backer & Bakh.f., Fl. Java 1: 476. 1963; Airy Shaw, Kew Bull. 26: 243. 1972, p.p. as to Peninsular colls.; Whitmore, Tree Fl. Malaya 2: 85. 1973, p.p. excl. C. adumbratus; Corner, Wayside Trees Mal., ed. 3: 283. 1988, p.p. excl. C. adumbratus; Chakrab. & N.P.Balakr., Bull. Bot. Surv. India 34: 22. 1997 (1992), p.p.; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 193,, fig. 45, plate X: 2. 2005.

 

   

 

Bushy tree to tree to 10 m tall, dbh to 20 cm, girth to 40 cm; bark grey brown, smooth, inner bark pink; young branchlets pubescent, glabrescent. Indumentum consisting of stellate to stellate-lepidote, hyaline hairs with a small brownish center (appearing silvery) on leaves and sepals, creamish-brown hairs on leaf veins and fruits, flat, sometimes with a central porrect radius, 0.2-0.3 mm in diam., with c. 15-17 free to partly fused radii. Stipules (2.5-)4-5 mm long, pubescent. Leaves alternate to apically crowded; petiole 5-12 cm long, densely pubescent; blade elliptic, 14-20 by 6-11 cm, index 1.5-2.3, chartaceous, base acute to obtuse but the very base distinctly cordate and slightly peltate, margin entire, apex short-acuminate, nearly glabrous above (few hairs in the very base), below completely and densely silvery-pubescent without visible surface and not glabrescent, brownish hairs only on the largest veins and on immature leaves; basal glands flat, sessile, 1-1.5 mm in diam., lateral on the abaxial midrib base, marginal glands absent; side veins 8-10 pairs, not triplinerved, veinlets visible. Inflorescences yellowish-green to silvery, never crowded, 12-25 cm long, with 7-12 pistillate flowers, without bisexual bracts; densely and persistently pubescent throughout; bracts 1-2 mm long, stiff, eglandular, caducous. Staminate flowers densely pubescent; pedicel 5-6 mm long; sepals 3 by 1.5 mm; petals 3.5 by 1 mm, whitish lanate; stamens c. 10-12, glabrous or with partly pubescent filaments. Pistillate flowers densely pubescent; pedicel 4-6 mm long (10-13 mm in fruit); sepals 4-5 by 1.5-2.5 mm, fused at the base, spreading at the apex, much longer than the ovary; petals absent or as tiny scales up to 1 by 0.3 mm long; ovary 2 mm long; stigmas 3-4 mm long, free at base, undivided for up to 1 mm at the base, once bifid apically. Fruits 12-16 by 12-16 mm, not sulcate, densely pubescent. Seeds flattened, 10-11 by 7-8 mm, ecarunculate.

    T h a i l a n d. PENINSULAR: Krabi (Ko Lanta), Nakhon Si Thammarat (Khao Luang, Garome Waterfalls), Songkhla (Boriphat Waterfalls, Ton Nga Chang), Narathiwat (Bacho, Waeng).

    D i s t r i b u t i o n. Thailand, W. Malesia: Malay Peninsula, Sumatra, Java (type), Lesser Sunda Islands, Borneo, Philippines.

    E c o l o g y.  Open areas, hill slopes and partly disturbed places in evergreen forest, secondary forest in rubber plantation, at rocky streams and roadsides. Altitude: 50-400 m. Flowering: April-June, September, December; fruiting: August-November, January. Inflorescences very fragrant and with much nectar.

    V e r n a c u l a r. Plao ngoen (เปล้าเงิน) (Pattani); mai lot (ไม้ลอด), plao (เปล้า) (Peninsular).

    N o t e s. C. argyratus is characterized by purely silvery-pubescent leaves without any brownish hairs when mature, usually cordate at the base, and a very constant fruit size of 12-16 mm. The name has often been misapplied to numerous Asian species with silvery-pubescent leaves. The true species does not occur in Thailand north of the Peninsula.

 

3. Croton bonplandianus Baill., Adansonia 4: 339. 1863-4; Mll.Arg. in DC., Prodr. 15, 2: 661. 1866 (under C. persicaria); Croizat, J. Bombay Nat. Hist. Soc. 41: 573. 1940; Radcl.-Sm., Fl. Pakistan 172: 43. 1986; Fl. Trop. East Afr., Euphorbiac. 1: 159. 1987; Bansiddhi, Nat. Hist. Bull. Siam Soc. 42: 79. 1994; Chakrab. & N.P.Balakr., Bull. Bot. Surv. India 34: 31. 1997 (1992); Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 195, plate X: 3. 2005. Croton sparsiflorus Morong, Ann. New York Acad. Sc. 7: 22. 1892; Burkill, Garden Bull. Singapore 1: 235. 1914.

 

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Erect herb or subshrub to 1 m tall; initially densely pubescent, later on glabrous. Indumentum consisting of stellate, whitish hairs (appearing as white dots), flat, 0.3-0.5 mm in diam., with (8-)10-15 free radii. Stipules c. 0.5 mm long, filiform, subglabrous. Leaves mostly pseudo-verticillate, sometimes alternate; petiole 0.5-1.2 cm long, initially densely pubescent, glabrescent; blade ovate-elliptic to lanceolate, 3-5.5 by 1-2 cm, index 1.5-3.5, membranous, base obtuse, margin serrate, apex acute to mucronate, with both sides of nearly same colour, initally pubescent on both sides, glabrescent; basal glands lateral on abaxial midrib base as a pair of prominent but sessile discs 0.3-0.5 mm in diam.; venation only visible below, side veins 6-7 pairs, basal pair different (triplinerved). Inflorescences creamy-white, 4-12 cm long, with 2-7 pistillate flowers, without bisexual bracts; sparsely pubescent to subglabrous except for the distinctly pubescent ovaries; bracts c. 1 mm long, with a distinct pair of pillow-shaped glands c. 0.5 mm in diam., in staminate part often eglandular. Staminate flowers subglabrous to glabrous outside; pedicel 1-1.5 mm long; sepals 1-1.25 by 1 mm; petals c. 1.5 by 0.5 mm; stamens 13-16, filaments glabrous. Pistillate flowers: pedicel nearly absent (c. 0.25 mm, 0.5 mm in fruit), subglabrous; sepals c. 1 mm long, subglabrous, shorter than the ovary; petals absent; ovary c. 1.5 mm long, very densely pubescent; stigmas free, 1.5-2 mm long, bifid for most (more than half) of their length. Fruits brownish-green, 5.5-6 by 4-4.5 mm, oblong, sulcate, thin-walled, initially densely pubescent but soon glabrescent. Seeds c. 4-5 by 2-3 mm, grey-blackish-brown, nearly smooth (finely rugulose), carunculate.

    T h a i l a n d. EASTERN: Nakhon Ratchasima (Sikhio); SOUTH-WESTERN: Kanchanaburi (Lao Khwan), Phetchaburi (Cha-Am), Prachuap Khiri Khan (Hua Hin, Muang); CENTRAL: Sing Buri, Suphan Buri (U Thong), Ang Thong (Chai Yo), Pra Nakhon Si Ayutthaya, Nakhon Pathom (Khampaeng Saen), Bangkok (Bang Khen); SOUTH-EASTERN: Chachoengsao (Pranoam Sarakham); PENINSULAR: Narathiwat (Tak Bai).

    D i s t r i b u t i o n. Native to S. America (from Bolivia to Argentina, type from Argentina); introduced and naturalizing in Africa (Kenya), South-East Asia from Pakistan to Laos, Malay Peninsula (incl. Singapore), Borneo, Sulawesi, and probably further.

    E c o l o g y. Weed on waste places, roadsides, paddy or sugar cane fields, seashores; on sand or sandy clay. Altitude: sea level to c. 100 m. Flowering and fruiting: April, August, September, December (the whole year through?).

    V e r n a c u l a r. Plao thung (เปล้าทุ่ง) (General).

 

4. Croton cascarilloides Raeusch., Nomencl. Bot. ed. 3: 280. 1797; Merr., Lingnan Sci. J. 13: 60. 1934; Trans. Amer. Philos. Soc., n.s. 24: 234. 1935; Croizat, J. Arnold Arbor. 23: 46. 1942; Airy Shaw, Kew Bull. 16: 344. 1963; Kew Bull. 26: 244. 1972; Whitmore, Tree Fl. Malaya 2: 84. 1973; P.H. H, Cyco Vitnam 2, 1: 299, fig. 4479. 1992; Y.T. Chang, Fl. Reipubl. Pop. Sin. 44(2): 127, pl. 29 fig. 1-3. 1996; Chakrab. & N.P.Balakr., Bull. Bot. Surv. India 34: 81. 1997 (1992); Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 197. 2005. Croton punctatus Lour., Fl. Cochinch: 581. 1790, nom. illeg. (non Jacq., Collectanea 1: 166. 1786); Mll.Arg. in DC., Prodr. 15, 2: 565. 1866; Gagnep. in Lecomte, Fl. Indo-Chine 5: 290. 1925. Croton cumingii Mll.Arg., Linnaea 34: 101. 1865; in DC., Prodr. 15, 2: 566. 1866; Craib, Contr. Fl. Siam: 190. 1912; Ridl., Fl. Malay Pen. 3: 261. 1924; Gagnep. in Lecomte, Fl. Indo-Chine 5: 264. 1925. Croton pierrei Gagnep., Bull. Soc. Bot. France 68: 558. 1922; in Lecomte, Fl. Indo-Chine 5: 265. 1925.

 

Shrub 0.5-2 m tall, dbh to 12 cm; bark thin, smooth, grey; densely pubescent, hardly glabrescent; Indumentum consisting of lepidote, hyaline hairs with a small yellowish-brownish center (appearing yellowish-silvery), completely brownish hairs scattered (on leaves) to dense (on floral parts), flat, 0.5-1.0 mm in diam., with (30-)50-70 fused radii. Stipules 4-6 mm long, densely pubescent. Leaves pseudo-verticillate apically, alternate on lower parts; petiole (0.3-)0.8-4 cm long, densely pubescent; blade elliptic to slightly obovate, 9-21 by 3.5-7 cm, index 1.8-3.6, chartaceous, base rounded to subcordate, margin entire, apex acuminate, glabrous above, below completely and densely silvery-pubescent without visible surface and not glabrescent, scattered darker hairs visible as distinct dots; basal glands as slightly elevated discs 0.2-0.8 mm in diam. lateral on the abaxial midrib base, additional marginal glands absent; side veins 8-15 pairs, below prominent but not differing in colour, not triplinerved, tertiary veins very indistinct. Inflorescences silvery-white to yellowish-brown, solitary or a few in an apical whorl, 0.5-2 cm long and with very few flowers only, with 2(-4) pistillate flowers, apically with c. 3 staminate flowers, the medium part usually naked with scars only, without bisexual bracts; densely brownish pubescent throughout, not glabrescent; bracts 2-3.5 by 1-1.5 mm, covering a whole flower, eglandular, soon caducous; 1 staminate flower per bract. Staminate flowers: pedicel c. 1 mm long; sepals c. 2 by 1.5 mm; petals c. 2 by 1.5 mm; stamens c. 13-15, glabrous. Pistillate flowers: pedicel c. 0.5 mm long (0.5-1 mm in fruit); sepals 2.5-3 by 1.5-2 mm, incurved, longer than the ovary; petals absent; ovary c. 2 mm long; stigmas 2-3 mm long, fused at the very base, filiform, bifid most of their length, apically slightly quadrifid, later on shed. Fruits green with brown scales, densely pubescent throughout, 4-5 by c. 5 mm, sulcate; stigmas shed and not present. Seeds flattened, c. 4 by 3.5-4 mm, ecarunculate.

    T h a i l a n d. NORTHERN: Lampang (Chae Son), Nakhon Sawan (Mae Wong); NORTH-EASTERN: Loei (Phu Luang); EASTERN: Chaiyaphum (Ban Nam Phrom), Nakhon Ratchasima (Khao Yai, Sakaerat); SOUTH-WESTERN: Uthai Thani (Thum Prayarpaishu), Kanchanaburi (Erawan Waterfalls, Khao Salop), Ratchaburi (Khao Nam Tok), Phetchaburi (Kaeng Krachan), Prachuap Khiri Khan (Bang Saphan, Huai Yang Waterfalls, Pran Buri, Sam Roi Yot); SOUTH-EASTERN: Prachin Buri (Khao Yai), Chon Buri (Chantaten Falls, Khao Khiao, Sattahip, Si Racha), Chanthaburi (Khao Soi Dao); PENINSULAR: Chumphon (Ko Tao), Surat Thani (Khao Phra Rahu, Yan Yao, Chaiya, Ko Samui), Phangnga (Khao Tam Thong Lang, Similan), Phuket (Ao Sane Beach), Krabi), Satun (Ko Kabeng, Ko Tarutao), Songkhla (Ton Nga Chang, Padang Besar), Yala (Banang Sata).

    D i s t r i b u t i o n. Japan (Ryukyu Islands), S. China, Indochina (type), Thailand, W. and C. Malesia (from the Malay Peninsula to Borneo, the Philippines, and the Moluccas, but excl. Java); not yet recorded for Burma.

    E c o l o g y. In primary dry evergreen or mixed evergreen/deciduous forest, bamboo-hardwood forest, secondary dipterocarp forest, on rocky slopes and outcrops, hills, also on streambanks, usually shaded, mostly collected on limestone, but also rarely on sandstone and basalt. Altitude: sea level to 600 m. Flowering and fruiting the whole year through. The flowers are slightly scented.

    V e r n a c u l a r. Ka-don hin (กะดอนหิน) (Loei); plao nam ngoen (เปล้าน้ำเงิน) (Prachuap Khiri Khan); plao lek (เปล้าแล็ก), plao ngoen (เปล้าเงิน) (Peninsular).

    U s e s. Bark and roots are used as an antipyretic.

 

5. Croton caudatus Geiseler, Croton. Monogr.: 73. 1807; Mll.Arg. in DC., Prodr. 15, 2: 599. 1866; Kurz, Forest Fl. Burma 2: 375. 1877; Hook.f., Fl. Brit. India 5: 388. 1887; Ridl., Fl. Malay Pen. 3: 259. 1924; Gagnep. in Lecomte, Fl. Indo-Chine 5: 286. 1925; Burkill, Dict. Econ. Prod. Malay Pen. 1: 689. 1935; Airy Shaw, Kew Bull. 26: 245. 1972; Whitmore, Tree Fl. Malaya 2: 85. 1973; P.H. H, Cyco Vitnam 2, 1: 295, fig. 4465. 1992; Y.T. Chang, Fl. Reipubl. Pop. Sin. 44(2): 133. 1996; Chakrab. & N.P.Balakr., Bull. Bot. Surv. India 34: 37. 1997 (1992); Welzen & Esser in Valkenburg & Bunyapraphatsara (eds.), PROSEA 12, 2, Medicinal and poisonous plants 2: 201. 2001; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 198. 2005. Croton denticulatus Blume, Bijdr. 12: 603. 1826, nom. illeg. (non Geiseler, Croton Monogr.: 72. 1807). Croton caudatus Geiseler  var. genuinus Mll.Arg. in DC., Prodr. 15, 2: 599. 1866, nom. inval. Croton caudatus Geiseler var. denticulatus (Blume) Mll.Arg. in DC., Prodr. 15, 2: 599. 1866. Croton caudatus Geiseler  var. caudatus: Kurz, Forest Fl. Burma 2: 375. 1877. Croton caudatus Geiseler var. malaccanus Hook.f., Fl. Brit. India 5: 389. 1887 (malaccana). Croton caudatus Geiseler var. harmandii Gagnep. in Lecomte, Fl. Indo-Chine 5: 286. 1925. Croton laccifer auct. non L.: Airy Shaw, Kew Bull. 26: 248. 1972.

 

Straggling shrub or woody climber up to 5 m tall; branching sometimes in apical whorls but otherwise alternate; young branchlets densely pubescent, slowly glabrescent. Indumentum consisting of yellowish-brown hairs, 0.3-1 mm in diam. on leaves (on the stems up to 0.1 mm small), stellate-dendritic and often porrect, with 6-12(-18) free radii. Stipules 2 mm long, filiform, quite glabrous. Leaves alternate; petiole 1-3 cm long, densely pubescent; blade ovate to elliptic, 3.5-9 by 2-4.5 cm, index 1.5-2.5, membranous to chartaceous, base cordate, sometimes nearly rounded, margin double-serrate to nearly entire, apex acute to subacuminate, initially distinctly brownish pubescent on both sides at least on the veins, usually also less densely between the veins, glabrescent; basal glands as one (rarely two) pairs of distinctly stalked (stalk 0.3-0.7 mm long) discs 0.7-1 mm in diam. lateral on the abaxial midrib base, additional smaller (0.2-0.7 mm) marginal glands common; side veins 5-8 pairs, triplinerved, veinlets distinct. Inflorescences greenish, 6-13 cm long, with 9-25 pistillate flowers, sometimes with bisexual bracts; densely yellowish-brown pubescent on the axis; bracts 2-3(-5) mm long, filiform, eglandular, pubescent, soon caducous and rarely seen. Staminate flowers: pedicel 3-8 mm long, densely pubescent; sepals 3 by 1.5 mm, sparsely pubescent outside; petals 2 by 1 mm, glabrous to lanate outside; stamens at least 18, glabrous. Pistillate flowers: pedicel 1.5 mm long (to 4 mm in fruit), densely hairy; sepals 2.5-3 by 1.5 mm, sparsely pubescent outside, nearly as long as the ovary; petals absent; ovary 3 mm long, densely yellowish-brown hispid; stigmas c. 5-7 mm long, not united at base, once divided along their whole length. Fruits greenish with brown hairs, 12-18 by 12-18 mm, not sulcate, surface densely brownish pubescent and slightly muriculate; pericarp very thick (2 mm) and woody. Seeds 13 by 10 mm, with scattered hairs, ecarunculate.

    T h a i l a n d. NORTHERN: Mae Hong Son; NORTH-EASTERN: Loei, Sakon Nakhon (Phanna Nikhom), Maha Sarakhan (Kosum Phisai); SOUTH-WESTERN: Prachuap Khiri Khan (Khao Luang); CENTRAL: Ang Thong (Wat Glahng), Krung Thep (Pakkret); SOUTH-EASTERN: Chachoengsao (Ban Krabok), Chanthaburi (Makham, Khao Sabap), Trat (Ko Chang); PENINSULAR: Surat Thani (Ta Chana), Nakhon Si Thammarat (Chong), Phatthalung (Khao Pu-Khao Ya), Satun, Songkhla (Ko Hong Hills, Tepa), Yala (Banang Sata), Narathiwat (Sungai Padi, Takbai).

    D i s t r i b u t i o n. Sri Lanka, India (type), Bhutan, Bangladesh, Burma, Thailand, Indochina, W. and C. Malesia (Malay Peninsula, Sumatra, Java, Borneo, the Philippines, Celebes and the Lesser Sunda Islands).

    E c o l o g y. In peat swamp forest, deciduous and evergreen forest, secondary forests and thickets, along rivers and streams. Altitude: sea level to 200(-700) m. Flowering (and fruiting?) the whole year through.

    V e r n a c u l a r. Krado hot bai khon (กระดอหดใบขน) (Southeastern); kho khlan (โคคลาน) (Chachoengsao); kurapia (Songkhla); kura pieak, ku raon, plao (เปล้า) (Peninsular).

    U s e s. A root decoction causes purging and is used medicinally for constipation in the Malay Peninsula. In Indonesia, dried bark is used to relieve stomach disorders.

    N o t e s. Airy Shaw (1972) reported C. laccifer from Thailand, based on a single collection (Kerr 5480 from Mae Hong Son, forest on limestone, 700 m). C. laccifer is very similar to C. caudatus; it differs from the latter in smaller fruits (c. 7-8 mm long) and non-climbing growth, and is otherwise known from Sri Lanka and S. India only. Kerr 5480 has staminate flowers only, and although described as tree it appears to be a climber. The leaves are narrower and denser tomentose than in typical C. caudatus, much like the type collection of C. laccifer. Nevertheless, in all characters studied it falls within the range of variation of C. caudatus (Kerr 10786 is even denser tomentose). Kerr 5480 can well be subsumed under C. caudatus, being the only record for Northern Thailand.

    Croton caudatus is remarkably constant in its fruits, being c. 15 mm over the whole considerable distribution range. Only few collections from Peninsular Thailand (Songkhla) have smaller (12 by 12 mm), obviously mature fruits.

 

6. Croton columnaris Airy Shaw, Kew Bull. 23: 69; Kew Bull. 26: 245. 1972; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 200, fig. 46. 2005.

 

 

Shrub to 2 m tall, dbh c. 2 cm, multi-stemmed; young branchlets distinctly pubescent, glabrescent. Indumentum consisting of stellate to slightly dendritic hairs, cream-brown to grey-brown hairs with a darker center, flat, 0.2-0.3 mm in diam., with c. 12-16 free radii. Stipules 1.5-3 mm long. Leaves alternate to crowded; petiole 1.2-3.5 cm long, densely pubescent, slowly glabrescent; blade elliptic and often rhomboid, (9-)13-21 by (2.5-)4-6 cm, index 2.6-3.6(-6.4), chartaceous, base acute to slightly obtuse with the very base rounded, margin distinctly serrate, the teeth 5-14 mm apart, apex acute to subacuminate, brighter below, glabrous above, subglabrous with few scattered hairs particularly on base and midrib below; basal glands flat, sessile but slightly prominent, 0.7-1 mm large, lateral on the abaxial midrib base or more often on the petiole apex; side veins 10-14 pairs, not triplinerved, veinlets distinct. Inflorescences greenish to yellow-green, solitary (or 2) apically, 3-8 cm long, usually bisexual, often with precocious fruiting (fruits develop when staminate flowers are still in bud), with 2-6 pistillate flowers, without bisexual bracts; distinctly pubescent throughout; bracts 0.7-1 mm long, less densely pubescent, eglandular or with a pair of flat glands up to 1 mm in diam., persistent. Staminate flowers: pedicel 2 mm long, with scattered to dense indumentum; sepals 2 by 1 mm, densely to sparsely pubescent; petals 2-2.5 by 1 mm, with few scattered hairs; stamens 10-12. Pistillate flowers: pedicel 0.7-1.5 mm long, densely pubescent; sepals 1.5-2 by 1 mm, densely to sparsely pubescent, shorter than or equalling the ovary; petals absent; ovary c. 2 mm long, densely pubescent; stigmas c. 4 mm long, basically united into a style column of 1-2 mm, otherwise nearly completely bifid. Fruits 7-8 by 10-10.5 mm, sulcate, with scattered but distinct hairs. Seeds 6-7 by 4.5 by 4.5 mm, with a small caruncle.

    T h a i l a n d. NORTHERN: Lamphun (Mae Ap), Lampang (Mae Het, Thoen), Sukhothai (Muang Kao Distr., Sawankhalok, type: Kerr 5899, holotype K, isotypes BK, BM, L), Phitsanulok (Chattrakan Waterfalls); SOUTH-WESTERN: Uthai Thani (Bansai).

    D i s t r i b u t i o n. Endemic.

    E c o l o g y. In dry deciduous oak forest, rocky hardwood forest slopes, open sandy places, over sandstone. Altitude: 100-600 m. Flowering and fruiting: January, March, April, September, November.

    V e r n a c u l a r. Plao noi (เปล้าน้อย) (Lampang); plao kham (เปล้าคำ) (Sukhothai).

 

7. Croton crassifolius Geiseler, Croton. Monogr.: 19. 1807; Merr., Trans. Amer. Philos. Soc., n.s. 24: 235. 1935; Airy Shaw, Kew Bull. 26: 245. 1972; P.H. H, Cyco Vitnam 2, 1: 293, fig. 4426. 1992; Y.T. Chang, Fl. Reipubl. Pop. Sin. 44(2): 130. 1996; Chakrab. & N.P.Balakr., Bull. Bot. Surv. India 34: 41, fig. 5. 1997 (1992); Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 202. 2005. Tridesmis tomentosa Lour., Fl. Cochinch.: 576. 1790. Croton tomentosus (Lour.) Mll.Arg., Linnaea 34: 107. 1865, nom. illeg. (non Link, Enum. Hort. Berol. Alt. 2: 406. 1822); in DC., Prodr. 15, 2: 588. 1866; Hook.f., Fl. Brit. India 5: 389. 1887; Craib, Contr. Fl. Siam: 190. 1912; Gagnep. in Lecomte, Fl. Indo-Chine 5: 262. 1925. Croton crozophoroides Kurz, J. Asiat. Soc. Bengal 42: 243. 1873 & Forest Fl. Burma 2: 372. 1877.

 

Low shrub to c. 1 m tall, with short and thick, crooked stem; branching irregular and rare; young branchlets densely pubescent, slowly glabrescent. Indumentum consisting of yellowish-brown hairs, stellate-dendritic and often porrect, 0.7-1(-1.5) mm in diam., to 2 mm long, with 6-8(-10) free radii. Stipules 10-15 mm long, filiform, fringed with conspicuous black capitate glands, densely pubsecent, quite persistent. Leaves crowded to alternate but never pseudo-verticillate; petiole 1.0-2.2 cm long, densely stellate-hispid; blade ovate to elliptic, 3.5-10 by 1.5-5 cm, index 2.0-3.0, chartaceous to coriaceous, base rounded to sometimes slightly cordate or obtuse, margin coarsely double-serrate to subentire, apex acute to obtuse, densely brownish pubescent (hispid-dendritic) on both sides, even more so on the veins, hardly glabrescent; basal glands as one (to two) pairs of stalked (stalk 0.2-0.5 mm long) to subsessile discs 0.2-0.5 mm in diam. lateral on the abaxial midrib base, additional smaller (0.2 mm) marginal glands common; side veins 6-8 pairs, triplinerved, veinlets visible. Inflorescences yellowish, 5-7 cm long, with 2-5 pistillate flowers, without bisexual bracts; densely yellowish-brown stellate-hispid on all outer surfaces; bracts 2-4 mm long, filiform but ciliate and fringed with conspicuous black-capitate glandular lobes, pubescent, persistent. Staminate flowers densely stellate-hispid throughout; pedicel 2-2.5 mm long; sepals c. 2.5 by 1.5 mm, partly fused; petals 2-2.5 by 1-1.5 mm; stamens 12-15 (sometimes described as 20-25), glabrous. Pistillate flowers densely stellate-hispid throughout; pedicel 1 mm long (2 mm in fruit); sepals 4-5 by 1-1.5 mm, longer than the ovary; petals absent; ovary 3 mm long; stigmas 3-4 mm long, not united at base, twice divided, once divided along their whole length and a second time in their upper half or more. Fruits 8-9 mm long, sulcate, surface stellate-hispid but otherwise smooth. Seeds 5-6 by 4 mm, with a distinct caruncle.

    T h a i l a n d. NORTHERN: Chiang Mai (Doi Suthep, Mae Rim, Mae Soi), Lamphun; NORTH-EASTERN: Loei (Srithan), Nong Khai (Phu Wua), Khon Kaen (Pu Wiang); EASTERN: Chaiyaphum (Pa -Hin Ngam), Nakhon Ratchasima (Bam Chun Saeng, Chan Tuek, Huai Thalaeng, Lat Bua Khao, Si Khio), Surin, Amnat Charoen (Chanuman Distr.), Ubon Ratchathani (Pha Taem).

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

    E c o l o g y. In the understorey of dry deciduous forest, dry and savannah-like dipterocarp forest, disturbed teak plantations, old clearings and roadsides, in open places and often among grasses; collected on granite, sandstone and limestone. Altitude: 100-850 m. Flowering: October-June; fruiting: October, December, April.

    V e r n a c u l a r. Pang khi (ปังคี) (Northern); phang khi noi (พังคีน้อย) (Eastern).

    U s e s. Root used in medicine to treat cholera, dysentery and to cure an inflamed throat. In combination with Clausenia harmandiana it is boiled and taken as antiflatulent.

 

8. Croton decalvatus Esser, Thai For. Bull. (Bot.) 29: 53. 2001; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 203, fig. 47. 2005. Croton thorelii auct. non Gagnep.: Airy Shaw, Kew Bull. 26: 250. 1972, p.p.

 

 

Shrub to 3 m tall; bark grey-brown, smooth; young branchlets densely pubescent at the top, soon glabrescent. Indumentum consisting of cream-brown hairs, flat, 0.3-0.6 mm (on pistillate flowers up to 0.75 mm) in diam., stellate with c. 20-25 free radii. Stipules 2-4 mm long, pubescent to subglabrous. Leaves crowded to pseudo-verticillate at nodes, alternate between; petiole 0.4-1.6 cm long, distinctly to indistinctly (but barely densely) pubescent; blade elliptic (hardly obovate), 12-30 by 3-8 cm, index 2.7-5.8, chartaceous, base acute with very base rounded-subcordate, margin distinctly serrate or double-serrate to subentire (teeth 4-8 mm apart), apex acute to subacuminate, brighter or same colour below, glabrous above, very sparsely pubescent below and soon glabrescent; basal glands sessile, flat to slightly elevated, 1-1.5 mm large, lateral on the abaxial midrib base, marginal glands absent; side veins 15-20 pairs, not triplinerved, veinlets visible. Inflorescences whitish-green, erect, (3-)8-12 cm long, with 8-20 pistillate flowers or purely staminate, without bisexual bracts; initially densely pubescent throughout but the bracts and sepals very soon glabrescent, the axis slowly glabrescent; bracts 3-5 by 1 mm, membranous, usually glabrous, eglandular, very soon and already in late bud caducous, bracteoles of c. 1 mm common. Staminate flowers: pedicel 2-3 mm long, distinctly pubescent and slowly glabrescent; sepals, 2.5 by 1-1.5 mm, soon nearly glabrous; petals 2.5 by 1 mm; stamens c. 12, glabrous. Pistillate flowers: pedicel (1.5-)2.5-3.5 mm long, densely pubescent (5-7 mm and subglabrous in fruit); sepals 4 by 1-1.5 mm, pubescent at base but nearly glabrous above, longer than the ovary; petals absent; ovary 2- mm long, densely pubescent; stigmas free at base, 4 mm long, bifid from the base, not quardifid. Fruits 7-9 mm long, slightly sulcate, surface sparsely pubescent but otherwise smooth, pericarp quite thin (0.5 mm). Seeds 6-7 by 4.5-5 mm, with a small caruncle.

    T h a i l a n d. NORTH-EASTERN: Sakon Nakhon (Phu Phan); EASTERN: Buri Ram (Nang Rong), Surin (Sangkha); SOUTH-EASTERN: Sa Kaeo (Khao Takrup, Pangsida, Roi Pi, type: Esser 98-105, holotype BKF, isotypes A, AAU, CMU, K, L, P), Prachinburi (Prachantakham), Chon Buri (Si Racha), Chanthaburi (Khao Phra Bat).

    D i s t r i b u t i o n. Endemic? To be expected in Cambodia.

    E c o l o g y. In disturbed evergreen and bamboo/deciduous forest, old clearings, along streams, shaded or exposed. Altitude: 100-500 m. Flowering and fruiting: August-February(-April).

 

9. Croton delpyi Gagnep., Bull. Soc. Bot. France 68: 548. 1922 & in Lecomte, Fl. Indo-Chine 5: 272. 1925; Airy Shaw, Kew Bull. 26: 246. 1972; P.H. H, Cyco Vitnam 2, 1: 300, fig. 4482. 1992; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 203. 2005.

 

Shrub or tree up to 10 m, girth to 50 cm; cut bark brownish, heartwood whitish; young branchlets densely pubescent, glabrescent. Indumentum consisting of yellowish-brown hairs, 0.3-0.5 mm (on ovaries to 0.7 mm) in diam., stellate to slightly dendritic, sometimes with a central porrect radius to 1 mm, with c. (12-)25-30 free radii. Stipules 3-7 mm long, densely pubescent. Leaves alternate to crowded; petiole 0.8-7 cm long, densely pubescent, hardly glabrescent; blade elliptic (to slightly obovate), 9-33 by 3-9 cm, index 3.0-4.5, chartaceous, base acute to obtuse with very base often rounded, margin shallowly but distinctly serrate (teeth c. 5-11 mm apart), apex acute to acuminate or rounded, brighter below, glabrous above, subglabrous with few scattered hairs particularly on the midrib below; basal glands sessile but slightly elevated, c. 0.7-1 mm large, lateral on the abaxial midrib base; side veins c. 11-21 pairs, not triplinerved, veinlets very distinct. Inflorescences pale yellow to whitish, usually several crowded in an apical whorl, 7-15 cm long, with 1-18 pistillate flowers, sometimes unisexual, sometimes with bisexual bracts; axis densely and persistently pubescent; bracts c. 2-3 mm long, subglabrous, eglandular, quite persistent. Staminate flowers: pedicel 2.5-3.5 mm long, densely pubescent; sepals 1.5-2 by 0.8-1.2 cm, pubescent at base, glabrescent at top; petals c. 2-3 by 1-1.5 mm; stamens 10 or 11, glabrous. Pistillate flowers: pedicel 1-3 mm long, densely pubescent; sepals 1.5-3 by 0.75-2 mm, subglabrous, nearly as long as or slightly longer than the ovary; petals absent; ovary 1.5-2.5 mm long, densely pubescent; stigmas 1.5-2.5 mm long, free, undivided for c. 0.5 mm at base or completely once divided. Fruits c. 7 mm long, sulcate, with scattered but distinct hairs. Seeds not studied.

    T h a i l a n d. SOUTH-EASTERN: Prachin Buri (Prachanthakham), Chon Buri (Si Racha), Rayong (Ban Phe), Chanthaburi (Makham, Tha Mai), Trat (Khao Saming, Taphan Hin). PENINSULAR: Surat Thani (Bang Bao), Krabi (Ko Lanta), Satun (Salat), Songkhla (Bam Klang, Boripat Falls, Ton Nga Chang, Hat Yai).

    D i s t r i b u t i o n. Thailand, Indochina (type), Malay Peninsula (excl. Singapore), to be expected in Burma.

    E c o l o g y. In open evergreen and mixed deciduous forest, transition evergreen-deciduous forest, rocky streamsides, in scrub forest and open disturbed roadside thicket. Altitude: sea level to 150 m. Flowering the whole year through; fruiting: February, December. The flowers are fragrant.

    V e r n a c u l a r. Plao yai (เปล้าใหญ่), nom nam khiao (นมน้ำเขียว) (Chon Buri); plao noi (เปล้าน้อย) (Chanthaburi); plao (เปล้า) (Southeastern); plao phai (Surat Thani).

    U s e s. For poles of houses, firewood.

 

10. Croton fluviatilis Esser, Thai For. Bull. (Bot.) 38: 33. 2010. Croton sp. 2: Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 225. 2005.

 

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Rheophytic shrub or small tree to 5 m tall; shoot apex distinctly pubescent, later sparsely pubescent to subglabrous. Indumentum consisting of lepidote, pale brown hairs, flat, ca. 0.2-0.3(-0.5) mm in diam., with ca. 30-40 completely to nearly fused radii. Stipules 3-5 mm long, pubescent. Leaves alternate, deciduous, turning yellowish orange before shedding; petiole 1-3.5 cm long, sparsely pubescent; blade linear, (10-)12-17 by 1.5-2.44 cm, index (5.0-)7.5-10.5, thinly chartaceous, base acute, margin indistinctly serrate to subentire (teeth 5-7 mm apart), apex acute-acuminate, upper surface glabrous, lower surface with few scattered hairs on the midvein below and otherwise subglabrous, hardly brighter than above, not glaucous; basal glands (on junction with the petiole) adaxial-lateral, flat, 0.7-1 mm in diam., adaxial marginal glands absent; side veins 11-16 pairs, hardly connected into loops (eucamptodromous), not to very indistinctly triplinerved. Inflorescences apical, solitary, 7-19 cm long, subglabrous to glabrous on axis and bracts; pistillate flowes 4-11, these with or without lateral staminate flowers (i.e. cymules bisexual or not); bracts of staminate flowers ovate, 2-3.5 by 1.5-2 mm, membranaceous. Staminate flowers 1-3(-4) per bract; pedicel 4-5 mm long, glabrous; sepals ca. 2.5 by 1.5 mm, slightly fused at base, apex acute to mucronate, glabrous outside but distinctly ciliate at apex; petals similar to sepals but narrower, ca. 2.5 by 0.5 mm; stamens 10-12, filaments 2-2.5 mm long, anthers ca. 0.6 mm long. Pistillate flowers with subglabrous pedicel ca. 2 mm long; sepals ca. 2 by 1 mm, apex acute to mucronate, quite glabrous; petals not seen; ovary ca. 1.5 mm long, smooth, densely pubescent; styles free, 3-5 mm long, bifid for more than half of length. Fruits with pedicel 4-8 mm long; capsule 5-7 by ca. 8 mm, smooth, distinctly sulcate, glabrescent with scattered hairs to subglabrous. Seeds 4-4.5 by 3-3.5 mm, ?ecarunculate.

    T h a i l a n d. EASTERN: Surin [Kap Choeng, trail from Chong Plot Tang to Wildlife Sanctuary Headquarters, Suddee, Trisarasri, Thanaros  Ritphet 3111 (holotype BKF!)]; Ubon Ratchathani (Kaeng Lam Duan; Phu Lone; Phu Chong Nayoi National Park, planted in Sa Kaeo RFD Centennial Botanical Garden).

    D i s t r i b u t i o n. Known from a few localities in eastern Thailand; likely to also occur in Cambodia.

    E c o l o g y. In areas of dry evergreen fores, but only along streams, in sandy soil over sandstone. Altitude 100-250 m. Flowering: February, March, June; fruiting: March, August.

    N o t es. 1. This new species is a rheophyte with narrow, linear leaf blades and is only found along stream banks. It is the only rheophyte among the 31 known Thai species. Although Croton is a large genus with at least 80 species in SE Asia, only few species with linear leaves are known from this area: Croton ensifolius Merr. (from the Malay Peninsula and Borneo) has very narrow leaf blades, only 7 mm wide, and mature leaves and inflorescences are glabrous; C. rheophyticus Airy Shaw (from Borneo) differs by smaller leaf blades up to 1.5 cm wide and stellate hairs (radii not fused); C. iteophyllus Radcl.-Sm. & Govaerts (= C. salicifolius Gagnep. non Geiseler, from Vietnam) has smaller (up to 1.2 cm wide) and completely glabrous leaf blades ang glabrous fruits.

2. Croton fluviatilis is also the only species among those from Thailand that combines lepidoter hairs with subglabrous inflorescences and fruits (the few other species with subglabrous inflorescences have stellate hairs, e.g., C. kerrii Airy Shaw). The orange colour of the leaves before they are shed is also noteworthy.

3. The species is possibly vulnerable (VU) according to the IUCN Red List categories, as it is known from few specimens from a restricted range, but probably not threatened immediately.

 

11. Croton griffithii Hook.f., Fl. Brit. India 5: 392. 1887; Ridl., Fl. Malay Pen. 3: 261. 1924; Burkill, Dict. Econ. Prod. Malay Pen. 1: 689. 1935; Airy Shaw, Kew Bull. 26: 246. 1972; Welzen & Esser in Valkenburg & Bunyapraphatsara (eds.), PROSEA 12, 2, Medicinal and poisonous plants 2: 201. 2001; Esser, Novon 12: 42. 2002; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 205. 2005. Croton confusus Gage, Rec. Bot. Surv. India 9: 237. 1922, p.p. excl. C. laevifolius. Croton laevifolius auct. non Bl.: Corner, Gard. Bull. Singapore 10: 294. 1939, p.p. excl. C. laevifolius; Whitmore, Tree Fl. Malaya 3: 85. 1973, p.p. excl. C. laevifolius; Corner, Wayside Trees Mal., ed. 3: 284. 1988, p.p. excl. C. laevifolius.

 

Shrub or tree to 12 m tall, girth to 80 cm; bark smooth, light greyish-brown; young branchlets densely pubescent, soon glabrescent. Indumentum consisting of stellate, pale-hyaline hairs (appearing pale-whitish-yellowish), flat, 0.2-0.4 (on flowers 0.5) mm in diam., with 12-15 free radii. Stipules 4 mm long, slightly pubescent. Leaves apically usually whorled but otherwise alternate; usually drying in a typical yellowish-brown colour; petiole 2.5-12 cm long, with scattered hairs to glabrous; blade elliptic, rarely slightly obovate, 11-27 by 4.5-12 cm, index 2.2-2.7, membranous to chartaceous, base (obtuse-)rounded to subcordate, margin shallowly serrate to subentire, apex rounded to mucronate, rarely acute to subacuminate, slightly brighter below, glabrous above, scatteredly but distinctly pubescent when young and soon to slowly glabrescent (similar to the petiole); basal glands sessile but distinctly (by c. 0.5 mm) elevated, 0.75-1.5 mm in diam., abaxial-lateral on the midrib base, marginal glands absent; side veins (9-)13-16 pairs, not triplinerved, veinlets visible. Inflorescences whitish, 7-30 cm long, often several grouped in an apical whorl, with 9-21 pistillate flowers, sometimes completely staminate or pistillate, sometimes with bisexual bracts; densely pubescent in bud but very soon glabrescent and therefore subglabrous on all surfaces when in flower except for the ovaries; bracts 1-2 mm long, eglandular, quite persistent. Staminate flowers subglabrous outside; pedicel 3-4 mm long; sepals 2 by 1-1.5 mm; petals 2 by 0.75 mm; stamens c. 10, glabrous. Pistillate flowers: pedicel 1-3 mm long, slightly pubescent; sepals 2 by 1 mm, slightly fused at base, slightly pubescent, longer than the ovary; petals not seen; ovary c. 2 mm long, very densely pale-yellowish pubescent; stigmas 3 mm long, slightly (0.5-1 mm) fused at base, undivided for 1-1.5 mm and once divided in the upper, c. half part. Fruits not seen for Thai collections, in the Malay Peninsula: pedicel glabrous; schizocarp 6.5-8 by 7-10 mm, deeply sulcate, with scattered hairs. Seeds not seen for Thai collections, in the Malay Peninsula: c. 7 by 6 mm, glabrous, ecarunculate.

    T h a i l a n d. PENINSULAR: Krabi (Ko Lanta), Trang (Khao Chong), Songkhla (Ton Satao), Narathiwat (Waeng).

    D i s t r i b u t i o n. Malay Peninsula (type) (incl. Singapore), Thailand, Borneo (Sabah, Sarawak).

    E c o l o g y. In evergreen forest and along streams, on granite bedrock. Altitude: 50-300 m. Flowering: February-April; fruiting: July, August. The flowers are fragrant.

    V e r n a c u l a r. Chik (จิก), plao (เปล้า) (Peninsular).

    U s e s. A decoction of the leaves is uses in Malaysia as bath after childbirth.

    N o t e. This species has been confused with C. laevifolius Blume by several authors; the latter shares indumentum and floral characters with C. griffithii, but differs in a different (darker) drying colour, narrower, basally obtuse leaves with adaxial-lateral, often stalked basal glands, and is not yet known from Thailand.

 

12. Croton hirtus LHer., Stirp. Nov.: 17, t. 9. 1785; Sinclair, Gard. Bull. Singapore 15: 1. 1956; Whitmore, Tree Fl. Malaya 2: 84. 1973; Radc.-Sm., Fl. Trop. East Afr., Euphorbiac. 1: 160. 1987; P.H. H, Cyco Vitnam 2, 1: 295, fig. 4467. 1992; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 206. 2005. Croton glandulosus L. var. hirtus (LHer.) Mll.Arg. in DC., Prodr. 15, 2: 684. 1866; Chakrab. & N.P.Balakr., Bull. Bot. Surv. India 34: 48. 1997 (1992). Croton glandulosus L. subsp. hirtus (LHer.) Croizat, Bull. Torrey Bot. Cl. 75: 401. 1948.

 

Erect herb up to 40 cm high; whole plant with hispid, irritating hairs, not glabrescent. Indumentum consisting of stellate-porrect, pale-brownish hairs, flat but usually with distinctly longer, central porrect radius, 0.5-2 mm in diam., with c. 10 (leaves: c. 6) free radii. Stipules 4-5 mm long, quite persistent, with some hairs, often ciliate-lobed. Leaves alternate below, but crowded to pseudo-verticillate on apical branches; petiole 0.2-2 cm long, stellate-hispid; blade ovate, up to 3.5-5 by 2-4 cm, index 1.0-1.6, chartaceous, base rounded-obtuse, margin coarsely double-serrate, apex acute, with scattered hairs above, densely stellate-hispid and slightly brighter below; basal glands lateral-abaxial on the petiole/blade junction, as 1-2 pairs of stalked discs (stalk c. 1 mm long, discs c. 0.3 mm in diam.), additional marginal glands absent; venation indistinct above, side veins 3-5 pairs, distinctly triplinerved, tertiary veins visible. Inflorescences green, 2-3 cm long, with 2-7 pistillate flowers, withoiut bisexual bracts; distinctly pubescent throughout; bracts 1-2 mm long, filiform, subglabrous, often ciliate with 2 or 3 pairs of filiform, gland-tipped, free or partly fused lobes at base. Staminate flowers distinctly hispid; pedicel c. 0.25 mm long; sepals c. 0.8 by 0.3 mm; petals c. 1 mm long; stamens c. 10, filaments subglabrous. Pistillate flowers distinctly hispid; pedicel very short (c. 0.2 mm) but soon elongating to 1-1.5 mm in fruit; sepals lineal, c. 2 by 0.5 mm, not to slightly longer than the ovary (3-3.5 by 0.5 mm in fruit); petals absent; ovary c. 1.5 mm long; stigmas free, 2 mm long, nearly completely divided. Fruits 3-3.5 by 3 mm, slighty sulcate, smooth, thin-walled, sparsely pubescent. Seeds c. 2.75 by 2 by 1 mm, variously yellow-brown/dark-brown/grey-brown mottled, shiny but minutely reticulate-foveolate, carunculate.

    T h a i l a n d. PENINSULAR: Songkhla (Hat Yai, Na Thawi), Narathiwat (Sungai Kolok).

    D i s t r i b u t i o n. Native to C. and S. America (from Mexico to Argentina; type from French Guiana and cultivated in Paris); introduced and naturalizing in W. and E. Africa, Sri Lanka, Thailand, Malesia from the Malay Peninsula to Papua New Guinea.

    E c o l o g y. Weed on waste places, old plantations, roadsides. Altitude: sea level to c. 60 m (outside Thailand to 600 m). Flowering and fruiting: August, October, December.

    V e r n a c u l a r. Plao lom luk (เปล้าล้มลุก) (Peninsular).

 

13. Croton hutchinsonianus Hosseus in Fedde, Repert. Spec. Nov. 10: 64. 1911; Craib, Bull. Misc. Inform. Kew 1911: 463. 1911; Contr. Fl. Siam: 190. 1912; Gagnep. in Lecomte, Fl. Indo-Chine 5: 278. 1925; Airy Shaw, Kew Bull. 26: 247. 1972; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 207, fig. 48. 2005.

 

 

Shrub or tree to 12 m tall, girth to 100 cm; bark thick and corky, with deep vertical furrows, greyish; sap thick and yellowish, turning red; young branchlets densely pubescent, glabrescent. Indumentum consisting of stellate hairs, yellowish-brown in the center with whitish radii (appearing cream-yellowish), flat and sometimes with a central porrect radius, 0.2-0.5 mm (on ovary up to 0.75 mm) in diam., with c. (10-)20-25 free radii. Stipules 3-5 mm long, densely pubescent. Leaves alternate albeit sometimes terminally crowded; petiole 3-8 cm long, densely pubescent but glabrescent; blade elliptic, rarely very slightly obovate, 13-28 by 5-12 cm, index 1.75-2.75, chartaceous, base obtuse to rounded(-subcordate), margin very indistinctly serrate to subentire, apex acute, mucronate, rounded or even emarginate but never acuminate, distinctly brighter below, glabrous above when mature, densely to scatteredly pubescent on the whole surface below (always densely pubescent on the midrib) with the surface partly visible, never glabrous; basal glands sessile to slightly elevated, c. 1 mm in diam., lateral on abaxial midrib base, marginal glands absent; side veins 14-21 pairs, not triplinerved, veinlets indistinct. Inflorescences whitish to yellowish-green, 10-30 cm long, with pistillate 6-14 flowers (if not completely staminate), sometimes with bisexual bracts; densely and persistently pubescent throughout; the axis often thick (2-3 mm base diam.) and grooved; bracts small, 1.5 by 1 mm in the staminate part (3 mm long in pistillate part), eglandular, caducous. Staminate flowers densely pubescent throughout; pedicel 2-5 mm long; sepals 2.5-3 by 1.5 mm; petals 2.5 by 1-1.5 mm, pubescent outside; stamens c. 10, glabrous or filaments slightly pubescent at base. Pistillate flowers densely pubescent throughout; pedicel 2-5(-8) mm long; sepals 3 by 1.5 mm, stiff, nearly as long as the ovary; petals often absent but sometimes present, 2 by 1 mm; ovary c. 3 mm long; stigmas 3-4 mm long, not fused at base, ?once divided along their whole length. Fruits c. 8 by 8 mm, sulcate, smooth, densely pubescent. Seeds not studied, but described as being 6 mm long, reddish.

    T h a i l a n d. NORTHERN: Chiang Mai (Doi Dao, Mae Taeng, Mae Klang), Chiang Rai (Chiangkham), Lampang (Doi Khuntan, Mae Chaeng), Phrae (Den Chai), Uttaradit (Thoet Phrakiat), Sukhothai (Khirimat, Muang Kao), Phitsanulok (Thung Salaeng Luang), Kamphaeng Phet (Mae Wong; type: Wang Chao, Hosseus 163, holotype M, isotypes A, B, BM, G, HBG, K, L n.v., M, MO, P); SOUTH-WESTERN: Uthai Thani (Huai Kha Khaeng), Kanchanaburi (Hin Lap, Thum Pha, Sadong, Sai Yok), Phetchaburi (Kaeng Krachan, Tung Luang); CENTRAL: Suphan Buri (U Thong).

    D i s t r i b u t i o n. Endemic (but to be expected in Burma).

    E c o l o g y. In degraded seasonal deciduous dipterocarp-oak forest, evergreen or deciduous, open and even savannah-like dry forest, scrub forest, rocky slopes. Altitude: 100-700 m. Flowering: October-February; fruiting: December-March. Flowers sweet scented.

    V e r n a c u l a r. Mae la lueat (แม่ลาเลือด) (Lampang); mueat hon (เหมือดฮ้อน), plao lueat (เปล้าเลือด) (Northern); plao (เปล้า), plao phae (เปล้าแพะ) (Phetchaburi).

 

14. Croton kerrii Airy Shaw, Kew Bull. 23: 71. 1969; Kew Bull. 26: 247. 1972; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 209, fig. 49. 2005. Croton hookeri auct. non Croizat: Airy Shaw, Kew Bull. 26: 246. 1972. Croton laevifolius auct. non Bl.: Craib, Bull. Misc. Inf. Kew 1911: 463. 1911; Contr. Fl. Siam: 190. 1912; Gagnep. in Lecomte, Fl. Indo-Chine 5: 289. 1925.

 

 

Shrub or treelet to 5 m tall; bark thin, shallowly vertically cracked, brown; young parts pubescent, soon glabrescent. Indumentum consisting of stellate, pale-brownish hairs, flat but sometimes with a short central, porrect radius, 0.3-0.5 mm in diam., with 13-17 free radii. Stipules 1-1.5 mm long, subglabrous. Leaves pseudo-verticillate at nodes, sometimes alternate on internodes; petiole 0.3-1.0(-3.0) cm long, initially pubescent, soon glabrescent; blade elliptic to slightly obovate, (4-)9-15 by 2-6 cm, index 2.0-4.3, chartaceous, base obtuse, margin indistinctly serrate to subentire (teeth 3-8 mm apart), apex acute to short-acuminate, mature blades glabrous or with few hairs on midrib, slightly brighter below; basal glands lateral on the abaxial midrib base but often visible from above, as distinctly stalked (stalk 1-2 mm long) discs 0.6 mm in diam.; side veins 9-12 pairs, basal veins slightly different but hardly triplinerved, smaller veinlets hardly visible. Inflorescences 2-7 cm long, white to yellow, with 1-6 pistillate flowers, sometimes purely staminate, without bisexual bracts; axis sparsely pubescent to glabrous; bracts 0.7-1.2 mm long, eglandular, persistent, subglabrous. Staminate flowers sparsely pubescent to glabrous outside; pedicels 1.5-2.5 mm long; sepals 1.5 by 0.8 mm; petals 1.5 by 0.5 mm; stamens c. 10, glabrous. Pistillate flowers: pedicel 1 mm long, sparsely pubescent; sepals 1-1.5(-2) by 0.7-1 mm, slightly pubescent (to subglabrous), as long as ovary; petals absent; ovary densely yellowish stellate-hispid; stigmas free, 1-2 mm long, bifid for more than half of their length, often completely. Fruits: pedicel 1.5-3 mm, subglabrous to glabrous; schizocarp 5-6 mm long, slightly sulcate, with scattered hairs to subglabrous. Seeds c. 5 by 4.5 by 4 cm, glabrous, ?ecarunculate.

    T h a i l a n d. NORTHERN: Chiang Mai (Doi Suthep), Uttaradit (Phu Soi Dao); NORTH-EASTERN: Phetchabun (Lom Sak), Loei (Phu Luang), Nong Khai (Bueng Kan, Chaiyaburi), Sakon Nakhon (Phu Phan, type: Kerr 8509, holotype K, isotypes A, BK, BM, L), Khon Kaen (Phu Khiao); EASTERN: Chaiyaphum (Chulaphorn Dam, Tung Kamang), Nakhon Ratchasima (Khao Yai), Ubon Ratchathani (Warinchamrap); CENTRAL: Saraburi (Khao Yai), Nakhon Nayok (Khao Yai); SOUTH-EASTERN: Prachin Buri (Khao Yai).

    D i s t r i b u t i o n. Endemic? To be expected in Laos.

    E c o l o g y. In disturbed or primary evergreen seasonal hardwood forest, dry evergreen forest, mixed deciduous forest, dry dipterocarp forest, along streams, open and grassy spots in degraded forests, over sandstone. Altitude: 200-1400 m. Flowering (and fruiting?): January-July, October-December.

    V e r n a c u l a r. Plao (เปล้า) (General).

 

15. Croton kongensis Gagnep., Bull. Soc. Bot. France 68: 555. 1922 & in Lecomte, Fl. Indo-Chine 5: 287. 1925; Croizat, J. Arnold Arbor. 21: 500. 1940; Airy Shaw, Kew Bull. 26: 247. 1972; Chakrab. & N.P.Balakr., Proc. Indian Acad. Sc. 92: 370, fig. 5. 1983; P.H. H, Cyco Vitnam 2, 1: 296, fig. 4468. 1992; Y.T. Chang, Fl. Reipubl. Pop. Sin. 44(2): 125, pl. 29 fig. 4. 1996; Chakrab. & N.P.Balakr., Bull. Bot. Surv. India 34: 56. 1997 (1992); Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 209. 2005.

 

Shrub or treelet to 5(-14) m tall, base diam. to 15(-30) mm; bark thin, creamy brown, quite smooth with fine vertical cracks; densely pubescent, hardly glabrescent. Indumentum consisting of dentate to dentate-lepidote, whitish-hyaline hairs with a small darker center, flat, 0.25-0.4 mm in diam., scattered larger hairs (0.4-0.7 mm) brown throughout, with c. 25-35 partly to mostly fused radii. Stipules 1.5-4 mm long, densely pubescent. Leaves alternate; petiole (0.5-)1.0-4.5 cm long, often considerably variable on one branch, densely pubescent, usually glandular; blade (elliptic to) ovate, (5-)9-17 by (2.5-)3.5-7 cm, index 2.0-2.9, chartaceous, base acute to obtuse (rarely rounded), margin entire, apex acuminate, with scattered hairs above (dense on venation), slowly glabrescent, below completely (brownish-)silvery pubescent without visible surface and not glabrescent, larger (c. 0.6 mm) and darker hairs scattered as brownish dots; basal glands flat (to slightly cup-shaped) abaxial-lateral on the petiole apex and visible from above, 0.8-1.1 mm in diam., marginal glands absent; side veins 7-9 pairs below the apex, very distinctly triplinerved with the basal veins originating from the base of the blade, tertiary veinlets indistinct. Inflorescences: (6-)10-28 cm long, with 7-9 pistillate flowers, often with bisexual bracts; densely pubescent on all parts, hardly glabrescent; bracts 1-3 mm long, eglandular, quite persistent. Staminate flowers: pedicel 0.8-1.5 mm long; sepals 1.5 mm long; petals of equal size; stamens c. 12. Pistillate flowers: pedicel c. 0.5-1 mm long (2-4 mm in fruit); sepals 2-4 by 1.5 mm; petals probably absent; ovary 1.5-2 by 2 mm long; stigmas c. 4 mm long, free, once bifid for nearly their whole length. Fruits 5 mm long, deeply sulcate, densely pubescent outside, slowly glabrescent. Seeds 3.5-4.5 by 3-3.5 mm, brownish-yellowish marmorated, carunculate.

    T h a i l a n d. NORTHERN: Chiang Mai (Mae Chaem, Muang Khong W of Doi Chieng Dao, Phrao), Chiang Rai (Mae Fa Luang), Uttaradit (Phu Soi Dao), Phitsanulok (Thung Salaeng Luang); NORTH-EASTERN: Loei (Na Haeo), Nong Khai (Phu Tok Noi, Phu Wua), Sakon Nakhon (Phu Phan), Nakhon Phanom (Phu Langka, Tha Uthen), Khon Kaen (Phu Khieo); EASTERN: Chaiyaphum (Phu Khiao, Ban Nam Phrom), Nakhon Ratchasima (Khao Yai, Sakaerat, Khao Laem); CENTRAL: Saraburi (Khao Khieo), Nakhon Nayok (Khao Yai); SOUTH-EASTERN: Sa Kaeo (Roi Pi Botanical Garden), Prachin Buri (Khao Yai), Trat (Ko Kut).

    D i s t r i b u t i o n. Burma, Thailand, Indo-China (type from Vietnam), SW China (Yunnan).

    E c o l o g y. In dry and savannah-like dipterocarp forest, dry and hill evergreen forest, disturbed seasonal evergreen hardwood forest, clearings, secondary vegetation, also with bamboos, on sandy soil, sandstone. Altitude: 15-1,200 m. Flowering: January-October; fruiting: April-December. Flowers fragrant.

    V e r n a c u l a r. Plao ngoen (เปล้าเงิน), plao nam ngoen (เปล้าน้ำเงิน) (General); plao noi (เปล้าน้อย) (Nong Khai); se-po-tu (เสปอตุ) (Karen-Chiang Mai).

    U s e s. The leaves are used in Indo-China for various stomach disorders, and a decoction is externally applied for furuncles and impetigo.

 

16. Croton kongkandanus Esser, Novon 12: 32. 2002; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 211. 2005.

 

Tree to 15 m tall, dbh to 25 cm; bark grey, smooth to very finely roughened and with prominent, scattered lenticels; young branchlets densely pubescent, glabrescent. Indumentum consisting of stellate to stellate-lepidote hairs (radii more fused on leaves) with a small brownish center, hyaline (appearing silvery) on the leaves, brownish only on leaf veins and floral parts, flat, sometimes with a porrect central radius, c. 0.2-0.3 mm in diam., with c. 20-30 free to partly fused radii. Stipules 7-20 mm long, densely pubescent. Leaves often in an apical whorl but basically alternate; petiole 2.5-5.5 cm long, densely pubescent; blade elliptic to slightly ovate, 11-19 by 5-8.5 cm, index 1.8-2.3, chartaceous, base obtuse with the very base cordate, margin entire, apex short-acuminate, soon glabrous above, below completely and densely silvery-pubescent without visible surface and not glabrescent, hairs quite uniform, brownish hairs only on largest veins; basal glands flat, sessile, 0.5-1 mm in diam., lateral on the abaxial midrib base, marginal glands absent; side veins 8-10 pairs, not triplinerved, veinlets visible on both surfaces. Inflorescences solitary, 8-10 cm long, 2-6 pistillate flowers, without bisexual bracts; densely and persistently pubescent throughout; bracts c. 1 mm long, eglandular, quite persistent. Staminate flowers densely pubescent; pedicel 1-1.5 mm long; sepals c. 2 by 1.5 mm; petals c. 2-2.5 by 1 mm; stamens 11, pubescent at base. Pistillate flowers densely pubescent; pedicel c. 1 mm long (3-4 mm in fruit); sepals c. 4-5 by 2-2.5 mm, longer than the ovary; petals 2 by 0.5 mm; ovary 2.5 mm long; style column short (c. 0.5 mm), stigmas 4-5 mm long, bifid on the apical c. 3 mm. Fruits 22-27 by 20-21 mm, often slightly obovoid, not sulcate, densely pubescent outside. Seeds flattened, 15-16 by 8-11 by 6 mm, sometimes slightly variegated, caruncle not seen.

    T h a i l a n d. NORTHERN: Chiang Mai (Doi Chiang Dao), Tak (Pha Wo), Phitsanulok (Sri Satchanalai); SOUTH-EASTERN: Chon Buri (Khao Khiao, type: Maxwell 76-443, holotype BK, isotype AAU), Chanthaburi (Khao Sabap).

    D i s t r i b u t i o n. Endemic.

    E c o l o g y. In mixed deciduous and evergreen, seasonal hardwood forest, disturbed evergreen forest, open or shaded; shale bedrock. Altitude: 200-650 m. Flowering: March; fruiting: July, August.

    V e r n a c u l a r. Mi la (มีลา) (Sukhothai).

 

17. Croton krabas Gagnep., Bull. Soc. Bot. France 68: 555. 1922 & in Lecomte, Fl. Indo-Chine 5: 286. 1925; Airy Shaw, Kew Bull. 26: 247. 1972; P.H. H, Cyco Vitnam 2, 1: 296, fig. 4469. 1992; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 212. 2005.

 

Straggling shrub to 3 m tall; branching rich, alternate; young branches densely pubescent, slowly glabrescent. Indumentum consisting of stellate-dendritic to porrect, whitish hairs with yellowish-brown center (on the leaves, then appearing white) or yellowish-brown throughout, 0.5-0.7 mm in diam., with c. 13-18 free radii. Stipules 2 mm long, entire, densely pubescent. Leaves sometimes in an apical whorl but otherwise alternate; petiole 0.8-2.0 cm long, densely pubescent; blade ovate, 2.5-5.5 by 1.5-3.5 cm, index 1.3-2.5, chartaceous, base cordate to rounded, margin distinctly serrate, apex acute, brownish pubescent with flat hairs mostly on the veins above, completely and densely whitish-cream pubescent below without visible surface, not glabrescent; basal glands as stalked (stalk 1 mm long) discs c. 1 mm in diam. lateral on the abaxial midrib base, sometimes smaller (c. 0.3 mm long) marginal glands present; venation usually impressed above, side veins 5-8 pairs, not triplinerved. Inflorescences pale yellowish, 4-9 cm long, with c. 6 pistillate flowers, without bisexual bracts; densely brownish pubescent throughout; bracts very early caducous, none seen. Staminate flowers densely pubescent; pedicel 2 mm long; sepals 2 by 1.5 mm; petals 2 by 1 mm; stamens 30 or more, glabrous. Pistillate flowers densely pubescent; pedicel 1 mm long or shorter; sepals 2.5-3 by 1 mm, longer than the ovary; petals absent; ovary 2 mm long; stigmas 3 mm long, not united at base, divided along their whole length. Fruits 7-8 mm long (for Indo-China described as being ovoid, 9-10 by 7 mm), densely pubescent, smooth. Seeds not studied, but in Indo-China 5 mm long, covered with pale lepidote hairs.

    T h a i l a n d. NORTHERN: Phitsanulok, Nakhon Sawan (Paknampho); NORTH-EASTERN: Kalasin (Khamalasai); EASTERN: Nakhon Ratchasima (Phimai), Surin (Tha Thum), Si Sa Ket (Kanthararom), Ubon Ratchathani (Phibun Mangsahan); CENTRAL: Chai Nat, Suphan Buri (Don Buang), Ang Thong.

    D i s t r i b u t i o n. Thailand, Laos, Cambodia (type), erroneously recorded for Borneo (Sabah).

    E c o l o g y. In evergreen scrub, on riverbanks or sandstone rocks in rivers, in rice fields, wet and swampy places. Altitude: 20-120 m. Flowering: March-July, December, January; fruiting: January, May, September.

    V e r n a c u l a r. Fai nam (ฝ้ายน้ำ) (Eastern); phrik na (พริกนา) (Suphanburi) (Central); sai khao (ทรายขาว) (Northern).

 

18. Croton lachnocarpus Benth., Hook. J. Bot. Kew Gard. Misc. 6: 5. 1854; Mll.Arg. in DC., Prodr. 15, 2: 624. 1866; P.H. H, Cyco Vitnam 2, 1: 296, fig. 4470. 1992; Y.T. Chang, Fl. Reipubl. Pop. Sin. 44(2): 131, pl. 31 fig. 6. 1996; Esser, Novon 12: 44. 2002; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 213. 2005. Croton calococcus Kurz, J. Asiat. Soc. Bengal 42: 242. 1873 & Forest Fl. Burma 2: 376. 1877; Gagnep. in Lecomte, Fl. Indo-Chine 5: 274. 1925; Airy Shaw, Kew Bull. 23: 73. 1969; Kew Bull. 26: 245. 1972; Chakrab. & N.P.Balakr., Bull. Bot. Surv. India 34: 34, fig. 3. 1997 (1992). Croton bonianus Gagnep., Bull. Soc. Bot. France 68: 549. 1922 & in Lecomte, Fl. Indo-Chine 5: 271. 1925; P.H. H, Cyco Vitnam 2, 1: 294, fig. 4464. 1992. Croton murex Croizat, J. Arnold Arbor. 23: 41. 1942. Croton trachycaulis Airy Shaw, Kew Bull. 23: 74. 1969; Kew Bull. 26: 250. 1972.

 

Thin shrub or treelet to 3 m tall, with thick root at stem base; branching alternate; stems grey-green; branches distinctly hispid, older ones glabrous. Indumentum consisting of stellate, pale- to yellow-brown hairs (appearing hyaline to brownish), flat but mostly with a distinct central porrect radius, 0.75-1 mm in diam. (0.2-1.5 mm on leaves), with 5-7 free radii, on the leaves often reduced the single central porrect-hispid radius of (0.5-)0.75-1.5 mm. Stipules 1-2 mm long, hispid. Leaves regularly alternate (never crowded); petiole 0.5-2.7 cm long, hispid; blade ovate to elliptic, 3.5-11 by 2.5-5.5 cm, index (1.4-)2.0-2.9, membranous, base rounded to cordate, margin distantly (teeth 4-10 mm apart) and shallowly to very deeply serrate, apex acute to subacuminate, with distinct, scattered, hispid hairs on both sides but more densely so below especially on the midrib, never glabrous, below only slightly brighter and usually a bit rough-granulate (not smooth); basal glands distinctly stalked (stipe 0.5-1 mm long), obconical without a distinct apical disc, lateral on the abaxial midrib base, additional similar but smaller marginal glands often present; side veins 5-8 pairs, slightly to distinctly triplinerved, tertiary veins visible. Inflorescences 4-10 cm long, with 3-11 pistillate flowers, without bisexual bracts; densely to scatteredly hispid throughout, not glabrescent; bracts 1-1.5 mm long, eglandular, persistent. Staminate flowers densely pubescent; pedicels 1-3 mm long; sepals and petals 1.2-1.7 by c. 1 mm; stamens c. 10. Pistillate flowers distinctly pubescent; pedicel 2-4 mm long (3-8 mm in fruit); sepals 3-6 by 1-2.5 mm, weakly membranous, quite free, longer than the ovary; petals absent; ovary 2 mm long, densely yellowish-brown stellate-hispid; stigmas free, 4-5 mm long, completely bifid. Fruits 6-7 mm long, no complete ones seen, thin-walled, densely to sparsely stellate-hispid with the hairs on shallow to distinct muriculi (surface never smooth). Seeds flattened, 5-6 by 4-5 by 3.5 mm, with a very small caruncle.

    T h a i l a n d. NORTHERN: Chiang Mai (see note); EASTERN: Nakhon Ratchasima (Pak Chong); SOUTH-WESTERN: Kanchanaburi (Erawan), Phetchaburi (Kaeng Krachan), Prachuap Khiri Khan (Sam Roi Yot, Thap Sakae, Kuiburi/Kao Yai, Huai Yang, type of C. trachycaulis: Put 3186, holotype K, isotypes A, BK, BM, L); PENINSULAR: Phatthalung (Khao Oktalu).

    D i s t r i b u t i o n. In this wide concept from Burma (type of C. calococcus) through Indo-China (type of C. murex) to China (type of C. lachnocarpus).

    E c o l o g y. In dry evergreen forest, disturbed deciduous forest, on clearings, on granite and limestone. Altitude: 50-300 m. Flowering: March-October; fruiting: March-November.

    V e r n a c u l a r. Khi on (ขี้อ้น) (Prachuap Khiri Khan).

    N o t e. The collection Maxwell 98-683 (Doi Suthep-Pui, Chiang Mai, 900 m) differs in larger leaves (22 by 6.5 cm, slightly obovate), stipules (2-4 mm long) and inflorescences (18 cm long), but agrees in all diagnostic characters. It is most probably the only record of C. lachnocarpus for Northern Thailand.

 

19. Croton longissimus Airy Shaw, Kew Bull. 23: 70. 1969; Kew Bull. 26: 248. 1972; Esser & Chayam., Thai For. Bull. (Bot.) 29: 56. 2001; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 214. 2005.

 

Shrub of unknown size; shoot apex distinctly pubescent but very soon glabrescent; flowering with mature leaves. Indumentum consisting of stellate, pale-brownish hairs, 0.2-0.4 mm in diam., flat, with c. 20 free radii. Stipules c. 2 mm long. Leaves alternate; petiole 0.7-1.5 cm long, with distinct but not dense hairs; blade narrowly elliptic to obovate, c. 11-18 by 3-4 cm, index 2.7-6.1, chartaceous, base acute to obtuse, margin serrate (teeth 1-4 mm apart), apex acute to subacuminate, slightly brighter below, glabrous above, subglabrous to slightly pubescent below; basal glands sessile, often in 2 pairs, flat, 0.75-1 mm in diam. and sometimes elongate-narrowed, mostly at least partly on the abaxial blade touching the midrib, marginal glands absent; side veins 14-16 pairs, not triplinerved, veinlets visible. Inflorescences greenish, solitary or surrounded by several buds, c. 2-4 cm long, proterogynous, with c. 2 pistillate flowers or fruits (precocious fruiting common), without bisexual bracts; densely and persistently pubescent throughout except for the bracts; bracts c. 1 mm long, sparsely pubescent, eglandular, persistent. Staminate flowers densely pubescent; pedicel 1-2 mm long; sepals 1-1.5 by 1 mm; petals 2 by 1 mm; stamens c. 10, glabrous or pubescent even on the anthers. Pistillate flowers densely pubescent; pedicel 1.5-2 mm long; sepals 1.5-2 by c. 1 mm, slightly fused at base, less densely but still distinctly pubescent; shorter than the ovary; petals absent; ovary 2.5-3 mm long; stigmas 2 mm long, free, undivided for c. 1 mm and once divided apically. Fruits 6 by 5.5 mm, sulcate, surface sparsely pubescent, smooth. Seeds 5 by 3 by 3 mm, no caruncle seen.

    T h a i l a n d. NORTHERN: Lamphun (Ban Muang Nga), Lampang (Me Ab, Thoen, type: Winit 671, holotype K, isotypes BK, L).

    D i s t r i b u t i o n. Endemic.

    E c o l o g y. Only known from cultivation. Flowering and fruiting: December.

    V e r n a c u l a r. Plao noi (เปล้าน้อย) (Lamphun).

    U s e s. The leaves are used medicinally (dried and crushed or as bath).

    N o t e. This species is known from three collections only (Bjrnland & Schumacher 21, 521, and the type), all cultivated in the same region. It might be a narrow-leaved cultivar of C. stellatopilosus (see Esser & Chayam., loc. cit.).

 

20. Croton mekongensis Gagnep., Bull. Soc. Bot. France 68: 558. 1922 & in Lecomte, Fl. Indo-Chine 5: 276, fig. 29.6-8. 1925; Airy Shaw, Kew Bull. 26: 249. 1972; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 215. 2005.

 

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Shrub to 3 m tall; young branches densely pubescent, later glabrescent. Indumentum consisting of dentate-lepidote to lepidote hairs, (yellowish-)whitish hairs without a darker center (appearing yellowish-silvery), flat, 0.2-0.4 mm in diam., with 30-40 fused to partly fused radii. Stipules 1-2 mm long, densely pubescent. Leaves partly pseudo-verticillate apically but most leaves alternate; petiole 0.2-0.9 cm long, densely pubescent; blade elliptic, 3.5-7 by 1-2.5 cm, index 3.1-4.0, chartaceous, base obtuse, margin entire, apex rounded to mucronate-subacuminate, glabrous above, completely and densely silvery pubescent without visible surface below and not glabrescent, mature leaves with hairs of homogeneous colour, without brown dots; basal glands sessile, flat, 0.2-0.3 mm in diam. and lateral on the abaxial midrib base, marginal glands absent; midrib distinct but additional venation nearly invisible and not different in colour, side veins c. 10 pairs, not triplinerved. Inflorescences 2-6 cm long, with 3-8 pistillate flowers, sometimes with bisexual bracts; densely pubescent throughout; bracts 1-2 mm long, triangular, eglandular, persistent. Staminate flowers: densely pubescent throughout; pedicel 1-1.5 mm long; sepals and petals c. 2 mm long, only seen in bud; stamens 11-12. Pistillate flowers densely pubescent throughout; pedicel 1-2.5 mm long; sepals 2-3 by 1-1.5 mm, longer than the ovary; petals absent; ovary c. 2 mm long; stigmas 2-2.5 mm long, not united at base, divided along their whole length. Fruits c. 4 mm long, shape unknown, densely pubescent, smooth. Seeds 4.5 by 2.5 mm, with scattered hairs, ecarunculate.

    T h a i l a n d. NORTHERN: Kamphaeng Phet, Nakhon Sawan (Paknampho).

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

    E c o l o g y. In high-grass savannah. Altitude: 15-50 m. Flowering: January, July, August; fruiting: August

    V e r n a c u l a r. Plao nam ngoen (เปล้าน้ำเงิน), phrik na (พริกนา) (Nakhon Sawan).

 

21. Croton phuquocensis Croizat, J. Arnold Arbor. 23: 44. 1942; P.H. H, Cyco Vitnam 2, 1: 302, fig. 4487. 1992; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 215. 2005. Croton leiophyllus auct. non Mll.Arg.: Gagnep. in Lecomte, Fl. Indo-Chine 5: 273. 1925

 

Tree to 5 m tall, girth to 30 cm; young branchlets with scattered hairs, glabrescent. Indumentum consisting of dentate-lepidote hairs (partly stellate-lepidote on floral parts), pale- to yellowish-brown, flat, c. 0.2 mm in diam., with c. 25-30 mostly fused radii. Stipules 1 mm long, glabrous. Leaves alternate to crowded; petiole 1.1-2.0 cm long, with scattered hairs to glabrous; blade elliptic, 5-8.5 by 1.2-2.2 cm, index 3.2-4.2, chartaceous, base acute, margin shallowly serrate (teeth 3-6 mm apart), apex acute-subacuminate, slightly brighter below, slightly pubescent below when young, later glabrous; basal glands sessile but distinctly elevated, c. 0.75 mm in diam., adaxial-lateral on the petiole apex, only visible from above, marginal glands absent; side veins c. 15 pairs, not triplinerved. Inflorescences whitish, c. 12 cm long, solitary, completely staminate in the single collection; completely glabrous; bracts 1.5 mm long, eglandular, quite persistent. Staminate flowers glabrous outside; pedicel 3-4 mm long; sepals 2 by 1-1.5 mm; petals 2 by 0.5 mm; stamens 10, glabrous. Pistillate flowers unknown in Thailand, in Vietnam numerous (c. 10), pedicels 2 mm long, slightly pubescent, sepals 2-2.5 by 1.5 mm, glabrous, longer than the ovary, petals absent, ovary very densely yellowish-brown pubescent, stigmas 1-1.5 mm long, once divided in the upper half. Fruits and seeds unknown.

    T h a i l a n d. EASTERN: Ubon Ratchathani (Sae Waterfalls).

    D i s t r i b u t i o n. Vietnam (type), to be expected in Laos.

    E c o l o g y. In swamp in evergreen forest. Altitude low. Flowering: February.

    V e r n a c u l a r. Mat (มาด).

    N o t e.  The single Thai collection (Phucomsaeng 28) is a perfect match for C. phuquocensis. This species itself is also very similar to several Malesian species with older names, in particular C. leiophyllus Mll.Arg. of the Philippines. This difficult complex requires further studies.

    The Thai record of C. leiophyllus sensu Airy Shaw, Kew Bull. 26: 248.1972, was based on Lakshnakara 712 from Pattani. This collection is similar to C. phuquocensis, but has larger leaves (14 by 6.5 cm), rounded at base, with lateral-abaxial basal glands, and slightly larger sepals of pistillate flowers. It might be different from both taxa (perhaps C. laevifolius Blume?), but the whole complex needs further study.

 

22. Croton poilanei Gagnep., Bull. Soc. Bot. France 68: 559. 1925 & in Lecomte, Fl. Indo-Chine 5: 270. 1925; Airy Shaw, Kew Bull. 26: 249. 1972; P.H. H, Cyco Vitnam 2, 1: 302, fig. 4488. 1992; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 216, plate XI: 1. 2005.

 

 

Shrub or tree to 10 m tall, girth up to 55 cm; bark pinkish brown, smooth with minute lenticels; young branchlets densely pubescent, slowly glabrescent. Indumentum consisting of lepidote, grey-yellowish-brown hairs, flat, 0.2-0.4 (on ovary up to 0.7) mm in diam., with c. 40-45 fused radii. Stipules 2-4 mm long, densely pubescent. Leaves alternate, the terminal ones crowded; petiole 1.5-7 cm long, densely pubescent, hardly glabrescent; blade elliptic, rarely slightly obovate, 17-37 by 7-13 cm, index 2.0-3.7, chartaceous, base acute to rounded, margin distinctly and often deeply serrate, the teeth (5-)7-13 mm apart, apex acute to rounded, of nearly same colour on both surfaces, glabrous above, glabrous to sparsely pubescent below, slightly more so on the midrib; basal glands sessile to slightly elevated, 1-1.5 mm in diam., lateral on the abaxial midrib base, marginal glands absent; side veins 16-21 pairs, not triplinerved, veinlets visible. Inflorescences whitish-green to yellowish with brownish hairs, 12-40 cm long, with 7-20 pistillate flowers (if not completely staminate), without bisexual bracts; densely and persistently pubescent on the axis and pedicels (very rarely axis subglabrous) but sepals glabrescent; axis conspicuously thick (3-4 mm base diam.) and grooved; bracts conspicuously large, 5 by 2 mm at base, 3 by 1 mm in the upper part, membranous, subglabrous, eglandular or sometimes with a pair of disc-shaped glands 1 mm in diam., caducous. Staminate flowers: pedicel 2-3 mm long, densely pubescent; sepals 2.5 by 1-1.5 mm, sparsely pubescent to subglabrous; petals 2.5-3 by 1 mm; stamens c. 10, glabrous. Pistillate flowers: pedicel 1-3 by 3 mm, often thicker than long, densely pubescent, usually with a pair of sessile glands at base; sepals 5-7 by 2-4 mm, membranous and often bent outwards, distinctly pubescent at base but glabrous in the upper part, longer than the ovary; petals present, 2-3 by 0.75-1 mm; ovary 2-3.5 mm long, densely pubescent; style column c. 1 mm long, stigmas 3-4 mm long, undivided for 0.5-2 mm, then once divided for c. 2 mm. Fruits c. 11 mm long, hardly sulcate, surface densely pubescent, smooth, pericarp quite thin (0.75 mm). Seeds 9 by 6 mm, ?ecarunculate.

    T h a i l a n d. NORTHERN: Nan (Santisuk), Lampang (Mae Pak, Mae Sin), Phitsanulok (Phu Hin Rong Kla, Thung Salaeng Luang), Kamphaeng Phet (Mae Prat); NORTH-EASTERN: Nong Khai (Bueng Kan, Phu Wua), Nakhon Phanom (Tha Uthen); EASTERN: Nakhon Ratchasima (Khao Yai, Sakaerat), Si Sa Ket (Kantharalak); CENTRAL: Nakhon Nayok; SOUTH-EASTERN: Sa Kaeo (Pang Sida), Prachinburi (Khao Yai), Chanthaburi (Makham), Trat (Ban Saphan Hin, Bo Rai, Ko Chang).

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

    E c o l o g y. In mixed deciduous forest, evergreen forest and open savannah-like forest, roadsides and secondary forest, on dry poor sand over sandstone. Altitude: sea level to 1,800 m. Flowering (and fruiting?) the whole year through. Flowers are scented.

    V e r n a c u l a r. Plao luang (เปล้าหลวง), plao lueat (เปล้าเลือด) (Lampang); plao (เปล้า), plao yai (เปล้าใหญ่) (Southeastern).

    U s e s. The bark is applied against stomach pain.

 

23. Croton poomae Esser, Thai For. Bull. (Bot.) 30: 1, fig. 1-2. 2002; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 217, plate XI: 3. 2005.

 

   

 

Tree to c. 10 m tall, unbranched at base; young branchlets densely pubescent. Indumentum consisting of stellate-lepidote to dentate-lepidote hairs, hyaline with small brown center (on leaves, appearing mostly silvery) or brownish throughout (on leaf venation below and on shoot apex), flat, 0.2-0.4 mm in diam., with c. 15-25 partly fused radii. Stipules (3-)8-12 mm long, pubescent. Leaves alternate; petiole (3-)8-17 cm long, densely pubescent; blade (narrowly) ovate, 15-28 by 5-8.5 cm, index 2.1-3.3, chartaceous, base obtuse with the very base slightly cordulate, margin entire, apex acute-acuminate, soon glabrous above, below densely and completely silvery-pubescent without visible surface and not glabrescent, scattered reddish-brown hairs on the whole surface and in particular on the venation; basal glands flat, sessile, c. 0.75 mm in diam., lateral on the midrib base, marginal glands absent; side veins 13-16 pairs below the apex, not to very slightly triplinerved, tertiary veins visible on both surfaces, percurrent, smaller veinlets hardly visible. Inflorescences often several in an apical whorl, densely cramish-brown pubescent throughout, 3-13(-20) cm long, bisexual with 2-7 pistillate flowers at base, all bracts unisexual; bracts ca. 1-1.5 mm long, eglandular, quite persistent. Staminate flowers densely pubescent outside; pedicel c. 1 mm long; sepals 3 by 1.5-2 mm; petals similar to sepals, ciliate; stamens 10-11, the anthers 1-1.2 mm long, filaments c. 2 mm long. Pistillate flowers densely pubescent outside; pedicel very short, less than 0.5 mm long; sepals 5 by 1.5 mm, distinctly longer than the ovary, slightly fused at base; petals obviously absent; ovary c. 3 mm long; stigmas 2-3 mm long, deeply bifid. Fruits: pedicel 1-2 mm long; schizocarp 15-17 mm long, not sulcate, brownish pubescent, smooth. Seeds flattened, 9.5 by 6.5 mm, caruncle not seen.

    T h a i l a n d. NORTH-EASTERN: Nong Khai (Phu Wua, type: Pooma et al. 2774, holotype BKF, isotype A, BKF, L n.v.).

    D i s t r i b u t i o n. Endemic? To be expected in Laos.

    E c o l o g y. In disturbed dry evergreen forest, over sandstone. Altitude: 200-300 m. Flowering: May; fruiting: August.

    N o t e. Although the fruit size of this species agrees with that of C. argyratus, the narrowly ovate leaf shape and the higher number of veins separate this species. The peculiar leaf shape is unique in SE Asian and Malesian Croton.

 

24. Croton robustus Kurz, J. Asiat. Soc. Bengal 42: 242. 1873 & Forest Fl. Burma 2: 372. 1877; Airy Shaw, Kew Bull. 26: 249. 1972, p.p. as to the synonym of C. siamensis; Chakrab. & N.P.Balakr., Bull. Bot. Surv. India 34: 64, 65, fig. 12. 1997 (1992); Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 217. 2005. Croton siamensis Craib, Bull. Misc. Inf. Kew 1918: 369. 1918; Gagnep. in Lecomte, Fl. Indo-Chine 5: 288. 1925; Airy Shaw, Kew Bull. 26: 249. 1972 (as syn.nov.).

 

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Shrub or treelet to 8 m, dbh 6 cm; young parts distinctly pubescent. Indumentum consisting stellate-lepidote hairs (dentate-lepidote to lepidote on leaves), yellowish-cream with a darker yellow to brown center, flat, 0.25-0.5 (on ovary to 0.8) mm in diam., with c. 20-30 largely fused radii. Stipules c. 2 by 0.5 mm, pubescent. Leaves alternate to crowded; petiole 1-3 cm long, densely pubescent; blade elliptic, 10-17 by 3-6 cm, index 2.3-3.5, chartaceous, base (obtuse-)acute, margin subentire with very indistinct teeth 5-10 mm apart, apex rounded to subacute, glabrous above, with few to scattered hairs below but hardly glabrous, distinctly brighter although not whitish below; basal glands sessile, flat, 0.7-1.2 mm in diam., lateral on the abaxial midrib base; side veins 12-19 pairs, not triplinerved, veinlets visible. Inflorescences 8-23 cm long, several (up to 10-14) in terminal clusters, with light yellow to grey-whitish flowers, usually bisexual with 6-21 pistillate flowers, both sexes flowering nearly simulteaneously, without bisexual bracts; densely pubescent throughout, hardly glabrescent; bracts 1.5-2 mm long, eglandular, sometimes with glabrescent tip, persistent. Staminate flowers pubescent throughout; pedicel to 1 mm long; sepals and petals both 2-2.5 by 1-1.25 mm; stamens c. 12. Pistillate flowers without lateral staminate flowers; pubescent throughout; pedicel 1(-2) mm long; sepals 2-3 by 1.5-2 mm, shorter than the ovary; petals c. 2 mm long, filiform, glabrous; stigmas 1.5-2 mm long, quite thick, free at base, mostly to completely bifid and usually apically quadrifid. Fruits 6 by 7-7.5 mm, sulcate, smooth, densely pubescent. Seeds not studied.

    T h a i l a n d. SOUTH-EASTERN: Prachinburi (Ban Non, Prachantakham), Chon Buri (Khao Khiao, Sattahip, Si Racha; syntypes of C. siamensis: kerr 2146, BM, K; collins 224, A, K; collins 239, K).

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

    E c o l o g y. Common on hills, in open sandy or rocky thickets, sandy-rocky hardwood forest slope, dry evergreen forest. Altitude: c. 30-160 m (outside of Thailand to 700 m). Flowering: May, October-February; fruiting: October.

    V e r n a c u l a r. Plao yai (เปล้าใหญ่) (Prachinburi).

 

25. Croton roxburghii N.P.Balakr., Bull. Bot. Surv. India 3: 39. 1962; Airy Shaw, Kew Bull. 32: 74. 1977; P.H. H, Cyco Vitnam 2, 1: 298, fig. 4475. 1992 (as roxburghianus); Chakrab. & N.P.Balakr., Bull. Bot. Surv. India 34: 67. 1997 (1992); Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 218. 2005. Croton oblongifolius Roxb., (Hort. Beng.: 69. 1814, nomen) Fl. Ind. ed. 1832, 3: 685. 1832, nom. illeg. (non Delile, Descr. Egypte, Hist. Nat.: 283. 1814, nec Spreng., Syst. Veg. 3: 850. 1826); Mll.Arg. in DC., Prodr. 15, 2: 573. 1866; Kurz, Forest Fl. Burma 2: 373. 1877; Hook.f., Fl. Brit. India 5: 386. 1887; Craib, Bull. Misc. Inform. Kew 1911: 464. 1911; Contr. Fl. Siam: 190. 1912; Gagnep. in Lecomte, Fl. Indo-Chine 5: 279. 1925; Airy Shaw, Kew Bull. 26: 249. 1972.

 

Shrub or tree up to 10(15) m tall, dbh 25 cm, deciduous; bark thin, smooth, cracked with age, grayish to tan, inner bark pink; branching mostly verticillate; young branchlets densely pubescent, glabrescent. Indumentum consisting of lepidote hairs (rarely stellate-lepidote on floral parts), pale-grey-brownish hairs, flat, 0.2-0.3 mm (on flowers 0.5 mm) in diam., with 30 or more largely to completely fused radii. Stipules 2 mm long, sparsely pubescent. Leaves alternate (sometimes only in an apical whorl); petiole 1.0-5.2 cm long, initially densely pubescent but soon glabrescent; blade elliptic, 10-32 by 4-12 cm, index 2.1-3.1, chartaceous, base acute to obtuse, margin distinctly serrate, the teeth 3-5(-7) mm apart, apex acute to rounded, only slightler brighter below, glabrous above, very sparsely pubescent to glabrous below; basal glands sessile, flat to slightly elevated, c. 1 mm large, lateral on the abaxial midrib base, marginal glands absent; side veins 15-18 pairs, not triplinerved, tertiaries visible. Inflorescences greenish-whitish, often several in an apical leafless whorl, erect, 9-36 cm long, with 9-23 pistillate flowers, sometimes completely staminate, without bisexual bracts; initially densely pubescent but axis soon glabrescent (not however the flowers); bracts 1-3 mm long, densely pubescent to glabrous, stiff, usually with a pair of disc-shaped, up to 1 mm large glands at base, slowly caducous. Staminate flowers: pedicel 2.5-5 mm long, densely pubescent; sepals 2.5-3 by 1.5 mm, more or less glabrescent; petals 3 by 1 mm; stamens 10-12, glabrous or variously pubescent (rarely even on the anthers). Pistillate flowers: pedicel 2-4 mm long (3-5 mm in fruit), densely pubescent; sepals 2.5-3 by 1.5-2 mm, densely pubescent on their whole length, as long as or slightly longer than the ovary; petals often absent, when present 2 by 0.5 mm; ovary 2-2.5 mm long, densely pubescent; stigmas 3-4 mm long, not fused at base, undivided for 0.25-1.5 mm (up to half of length), once divided in the apical part. Fruits 6-7 by 6-7 mm, sulcate, surface sparsely but distinctly pubescent but otherweise smooth; pericarp quite thick. Seeds c. 6 by 4 mm, with a small caruncle.

    T h a i l a n d. NORTHERN: Mae Hong Son, Chiang Mai, Chiang Rai, Phayao, Nan, Lamphun, Lampang, Phrae, Tak, Sukothai, Phitsanulok, Kamphaeng Phet, Nakhon Sawan; NORTH-EASTERN: Phetchabun, Loei, Nong Khai, Sakon Nakhon, Nakhon Phanom, Mukdahan; EASTERN: Chaiyaphum, Nakhon Ratchasima; SOUTH-WESTERN: Uthai Thani, Kanchanaburi, Phetchaburi, Prachuap Khiri Khan; CENTRAL: Saraburi, Nakhon Nayok; SOUTH-EASTERN: Sa Kaeo, Chanthaburi.

    D i s t r i b u t i o n. India (type from Calcutta), Nepal, Bhutan, Bangladesh, Burma, Thailand, Laos, Cambodia, Vietnam.

    E c o l o g y. In mixed and dry deciduous forest, mixed evergreen/deciduous hardwood forest, dipterocarp-oak forest, disturbed hill and dry evergreen forest, Imperata or bamboo vegetation, fire-prone areas, secondary growth, road sides and old clearings, rocky slopes, dry or at streams, over limestone, sandstone, basalt or granite. Altitude: 10-950 m. Flowering: November-March (May); fruiting: January-April. The flowers are scented or with foetid odor.

    V e r n a c u l a r. Plao (เปล้า), plao yai (เปล้าใหญ่) (General); chi-mae-chi-cha, chi-mia-chi-yat-apa (Akha-Chiang Rai); say-ga-wa (Karen-Lamphun); plao luang (เปล้าหลวง) (Northern); khwa-wu (ควะวู) (Karen-Kanchanaburi); plao hua kwan (เปล้าห้วขวาิน) (Prachuap Khiri Khan).

    U s e s.  Leaves and heartwood used medicinally, e.g., externally for sprains. Pounded leaves are used for insect bites by the Akha; the boiled leaves give a bath for women after giving birth (by Karen, mixed with Zingiber, Antidesma, etc.), breathing of the boiling leaves helps recovering from fever, and mashed leaves together with salt, Cymbogon etc. are used as plaster for broken bones by the Lahu. The seed oil is purgative.

 

26. Croton sepalinus Airy Shaw, Kew Bull. 25: 514. 1971; Kew Bull. 26: 250. 1972; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 219. 2005. Croton argyratus var. microcarpus Gagnep. in Lecomte, Fl. Indo-Chine 5: 277. 1925; Croizat, J. Arnold Arbor. 23: 42. 1942; Airy Shaw, Kew Bull. 26: 244. 1972. ? Croton argyratus auct. non Blume: Kurz, Forest Fl. Burma 2: 372. 1877.

 

Shrub to treelet, to 10 m tall; younger parts densely silvery-brownish pubescent. Indumentum consisting of dentate-lepidote hairs, hyaline with a small brownish center (on leaves, appearing silvery) or brownish throughout (partly on leaves, in particular veins, dense on floral parts), flat, 0.2-0.3 mm in diam., with c. 25-30 partially fused radii. Stipules 5-8 mm long, pubescent. Leaves crowded but hardly verticillate; petiole 0.8-6 cm long, densely pubescent; blade elliptic to very slightly ovate or obovate, 8-21 by 3-7.5 cm, index 2.1-3.4(-4.0), membranous to chartaceous, base acute to rounded with the very base slightly and indistinctly cordate, margin entire, apex acuminate, glabrous above, completely and densely silvery-pubescent below without visible surface, with scattered darker hairs visible as reddish-brown dots; basal glands sessile, flat, 0.5-0.7 mm in diam., lateral on the abaxial midrib base, marginal glands absent; venation distinctly darker (by brownish hairs) below, side veins 6-8(-11) pairs below the apex, slightly triplinerved, tertiary veinlets visible. Inflorescences yellowish, usually solitary, 1.5-5.5 cm long, with 1-3 pistillate flowers, without bisexual bracts; densely brownish-silvery-pubescent throughout; bracts 1 mm long, eglandular, persistent. Staminate flowers densely pubescent throughout; pedicel 1 mm long; sepals and petals both c. 2-2.5 by 1 mm; stamens c. 12. Pistillate flowers densely pubescent throughout; pedicel 1-1.5(-2) mm long; sepals 2.5-5(-7) by 1-2.5 mm [3.5-5(-14) by 1.5-2(-3) mm in fruit], longer than the ovary; petals absent; ovary c. 2 by 2 mm; stigmas 2-5 mm long, free, bifid on nearly their whole length, filiform. Fruits c. 7 mm long, smooth, with scattered hairs. Seeds flattened, c. 6.5 by 5.5 by 3.5 mm, with scattered hairs, with a small caruncle.

    T h a i l a n d. SOUTH-WESTERN: Kanchanaburi (E. of Sangkhla), Prachuap Khiri Khan (Mueang Pran and Mont Luang, types of var. microcarpus: pierre s.n., P; Bang Saphan Yai); CENTRAL: Lop Buri (Chaibadan, type: Kerr 8024, holotype K, isotypes BK, BM, L); SOUTH-EASTERN: Trat (Ban Saphan Hin, Huai Raing); PENINSULAR: Chumphon (Paknam), Surat Thani (Kantuli, Na San, Tha Chang, Takuapa), Ranong, Phangnga (Ban Kampuam), Phuket (Thalang), Phatthalung (Tha Mot), Satun (Ko Tarutao).

    D i s t r i b u t i o n. Endemic? To be expected in Burma.

    E c o l o g y. In evergreen forest, forest margins and secondary forest, on streambanks. Altitude: 40-800 m. Flowering: January-April, June-October; fruiting: April, August, September. Flowers are fragrant.

    V e r n a c u l a r. Plao ngoen (เปล้าเงิน) (Peninsular).

    N o t e s. 1. The holotype in Kew shows remarkably large sepals of the pistillate flowers (7 by 2.5 mm) and fruits (10-14 by 2.5-3 mm). In all other characters it agrees well with additional collections with smaller sepals. These sepals may be more an exception than a specific character.

    2. Plants collected in Trat province differ in narrower leaves (index 3.0-4.0) from typical plants, which is probably not a sufficient difference for separation.

 

27. Croton stellatopilosus Ohba, J. Jap. Bot. 55: 97. 1980; Chakrab. & N.P.Balakr., Bull. Bot. Surv. India 34: 70. 1997 (1992; under C. sublyratus); Esser & Chayam., Thai For. Bull. (Bot.) 29: 57. 2001; Welzen & Esser in Valkenburg & Bunyapraphatsara (eds.), PROSEA 12, 2, Medicinal and poisonous plants 2: 202. 2001; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 220, plate XI: 2. 2005. Croton sublyratus auct. non Kurz: Airy Shaw, Kew Bull. 26: 250. 1972.

 

 

Shrub to 6 m tall, dbh 8 cm, branching from base; younger parts distinctly pubescent; flowering with mature leaves. Indumentum consisting of stellate-dendritic, cream-yellowish-brown hairs with a slightly darker center, not flat, 0.2-0.8 mm in diam., with 10-15 (on leaves 6-10) free radii. Stipules 3-4 mm long, densely pubescent. Leaves crowded but not pseudo-verticillate; petiole 0.5-2.5 cm long, distinctly but not densely pubescent at least on younger leaves; blade obovate and sometimes constricted near base, rarely nearly elliptic, 6-18 by 3-7 cm, index 2.0-4.0, chartaceous, base attenuate but very base always rounded, margin serrate (teeth c. 5 mm apart), apex acute to short-acuminate, glabrous above, with scattered and distinct but not dense hairs below, brighter below; basal glands sessile, flat, 0.8-1 mm in diam. and often elongate-narrowed, partly to completely on the blade very close to the petiole rather than on the petiole, few marginal glands sometimes present, small (c. 0.3 mm diam.), sessile; side veins 8-14 pairs, the basal pair slightly different (angle more acute), tertiary veins visible. Inflorescences whitish, 7-10 cm long, most often collected as stiff and dense, erect buds sometimes on a bent stalk of 1-2.5 cm long, distinctly proterogynous and often the apical, shorter staminate part still in bud when the lower pistillate part is already in flower or even in fruit (precocious fruiting), with 4-10 pistillate flowers, without bisexual bracts; with scattered and distinct indumentum on all parts, slowly glabrescent; bracts 1.5-2 mm long, eglandular, pubescent, caducous. Staminate flowers densely pubescent throughout; pedicel 2-6 mm long; sepals and petals both 2.5 by 1 mm; stamens 10, glabrous or with few hairs at base. Pistillate flower densely pubescent throughout; pedicel 4-6 mm long (-8 mm in fruit); sepals 3 by 1.5 mm, as long as the ovary; petals not seen; stigmas 3 mm long, free, undivided in the lower half and once divided apically. Fruits 5 by 6 mm, smooth to very slightly muriculate, sulcate, quite thin-walled, sparsely pubescent to subglabrous. Seeds 4 by 2.5 mm, with a very small caruncle.

    T h a i l a n d. CENTRAL: Lop Buri (Khao Thungna); SOUTH-EASTERN: Sa Kaeo (Roi Pi Botanical Garden), Prachin Buri (Kabinburi, type: Ogiso & Phromdej 229, holotype TI), Chachoengsao, Chon Buri (Chantaten Falls, Khao Khiao). Also cultivated, e.g. in Chiang Mai, Bangkok, Saraburi.

    D i s t r i b u t i o n---Endemic? To be expected in Cambodia.

    E c o l o g y. In rock crevices and rocky deciduous forest, mixed bamboo forest, dry evergreen forest, on roadside. Altitude: 30-500 m. Flowering and fruiting: December-February.

    V e r n a c u l a r. Plao noi (เปล้าน้อย) (General).

    U s e s. Medicinally used, and therefore often cultivated. This species is currently under active research in Thailand as a source of a drug against peptic ulcer (Plaunatol), and to stop stomach bleeding (in particular the leaves). Stem and bark are antidiarrheal and normalize menstruation. The flowers are antihelmintic. A tonic helps women who cannot eat, and after giving birth.

 

28. Croton thorelii Gagnep., Bull. Soc. Bot. France 68: 560. 1922; in Lecomte, Fl. Indo-Chine 5: 264, fig. 28.8-10. 1925; Airy Shaw, Kew Bull. 26: 250. 1972, p.p. excl. C. decalvatus; P.H. H, Cyco Vitnam 2, 1: 293, fig. 4460. 1992; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 221. 2005.

 

Tree to 8 m tall, bark brown, shallowly fissured; young branchlets densely pubescent, glabrescent. Indumentum consisting of stellate to stellate-lepidote, yellowish-creamish hairs with paler radii, flat, 0.2-0.3 mm in diam., with c. 18-25 hardly to partially fused radii. Stipules 1 mm long, pubescent. Leaves irregularly crowded to pseudo-verticillate, a few leaves alternate; petiole 0.3-0.9 cm long, densely pubescent, slowly glabrescent; blade elliptic to slightly obovate, 10-20 by 2.5-4.5 cm, index 2.8-6.0, chartaceous, base acute with very base rounded-subcordate, margin distinctly serrate to subentire (teeth 5-15 mm apart), apex acute to subacuminate, of same colour on both surfaces, glabrous above, very sparsely pubescent below and soon glabrescent; basal glands sessile, flat to slightly elevated, c. 0.75 mm large, lateral on the abaxial midrib base, marginal glands absent; side veins 10-24 pairs, not triplinerved, tertiaries visible. Inflorescences whitish-green, 2-12 cm long, with 1-2 pistillate flowers, sometimes completely staminate, without bisexual bracts; densely pubescent throughout with only the bracts sometimes glabrescent; bracts 1.5-2 by 1 mm, stiff, eglandular or biglandular inside, persistent. Staminate flowers densely pubescent; pedicel 1-1.5 mm long; sepals c. 3 by 1-1.25 mm; petals 2.5 by 1 mm, pubescent throughout; stamens c. 12. Pistillate flowers densely pubescent; pedicel 1-1.5 mm long (2.5-3 mm in fruit); sepals c. 2.5 by 1 mm, nearly as long as the ovary; petals absent; ovary 2-3 mm long, densely pubescent; styles free, stigmas 1.5-2 mm long, bifid from nearly their base, their apex often flattened and bifid again (quadrifid). Fruits not seen, the remaining columella 5-5.5 mm long. Seeds not seen.

    T h a i l a n d. NORTH-EASTERN: Sakon Nakhon (Phu Phan), Nakhon Phanom; EASTERN: Chaiyaphum (Nafoi); SOUTH-EASTERN: Prachin Buri (Kabin Buri), Sra Kaeo (Aranyaprathet, Krabin); PENINSULAR: Ranong (Ngao Waterfall).

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

    E c o l o g y. In dry evergreen forest, on rocky sites along streams. Altitude: 50-500 m. Flowering: September-April.

    V e r n a c u l a r. Plao noi (เปล้าน้อย), plao tawan (เปล้าตะวัน), plao tha po (เปล้าท่าโพ), ta-kri-num (Southeastern).

 

29. Croton tiglium L., Sp. Pl.: 1004. 1753; Mll.Arg. in DC., Prodr. 15, 2: 600. 1866; Kurz, Forest Fl. Burma 2: 374. 1877; Ridl., Fl. Malay Pen. 3: 262. 1924; Gagnep. in Lecomte, Fl. Indo-Chine 5: 285. 1925; Burkill, Dict. Econ. Prod. Malay Pen. 1: 690. 1935; Airy Shaw, Kew Bull. 26: 250. 1972; Whitmore, Tree Fl. Malaya 2: 84. 1973; Corner, Wayside Trees Mal., ed. 3: 284. 1988; Chakrab. & N.P.Balakr., J. Econ. Tax. Bot. 12: 367. 1988; P.H. H, Cyco Vitnam 2, 1: 298, fig. 4476. 1992; Y.T. Chang, Fl. Reipubl. Pop. Sin. 44(2): 133. 1996; Chakrab. & N.P.Balakr., Bull. Bot. Surv. India 34: 72. 1997 (1992); Welzen & Esser in Valkenburg & Bunyapraphatsara (eds.), PROSEA 12, 2, Medicinal and poisonous plants 2: 202, fig. 2001; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 222. 2005. Croton birmanicus Mll.Arg., Linnaea 34: 112. 1865 & in DC. Prodr. 15, 2:601. 1866; Airy Shaw, Kew Bull. 23: 72. 1969; Kew Bull. 26: 244. 1972; Chakrab. & N.P.Balakr., J. Econ. Tax. Bot. 12: 493. 1988, Bull. Bot. Surv. India 34: 28, fig.2. 1997 (1992). Croton himalaicus D.G.Long, Notes Royal Bot. Gard. Edinb. 44: 170. 1986; Chakrab. & N.P.Balakr., J. Econ. Tax. Bot. 12: 367. 1988.

 

Shrub or treelet to 6 m, branched from base, bark grey-green to tan, slightly roughened; branching crowded but usually not truely verticillate; young branchlets with scattered hairs, soon glabrescent. Indumentum consisting of stellate, yellowish-pale-brown hairs, often with a short central, porrect radius, 0.3-0.8 mm in diam., with 7-13 free radii. Stipules 0.5-1 mm long, subglabrous, caducous. Leaves alternate; petiole (1.2-)2.5-4.0 cm long, with scattered hairs or subglabrous; blade ovate-elliptic, 6-12 by 4-9 cm, index 1.2-2.0, membranous, base obtuse to subcordate with very base attenuate, margin shallowly serrate to subentire (teeth 2-5 mm apart), apex subacute to acuminate, slightly brighter below, with scattered hairs to subglabrous on both surfaces, sometimes densely pubescent on larger veins below; basal glands 0.75-1 mm in diam. and sessile to distinctly (by up to 3 mm) stalked, always lateral on the basal leaf margin close to but not on the midrib, marginal teeth often topped by small glandular tissue but without distinct additional glands; side veins (3-)4-6 pairs, very distinctly triplinerved. Inflorescences yellowish-green to whitish, erect, 7-15 cm long, with 2-15 pistillate flowers, often with bisexual bracts; the axis with scattered but distinct hairs or subglabrous; bracts 2-3(-4) by 0.5-1 mm, quite glabrous, eglandular, caducous to persistent. Staminate flowers subglabrous outside; pedicel 3 mm long; sepals 2.5-4 by 1.5 mm; petals 2 by 1 mm; stamens c. 12-15, glabrous. Pistillate flowers: pedicel 2-4 mm long (6 mm in fruit), distinctly pubescent; sepals 2.5-5 by 1-2 mm, slightly fused at base, subglabrous to slightly pubescent, slightly to distinctly longer than the ovary, membranous and usually spreading; petals absent; ovary 2.5 mm long, densely pubescent; stigmas 4-5 mm long, free, undivided for c. 1 mm at base or not at all, once bifid in the larger upper. Fruits 13-20 mm long, sulcate, surface subglabrous and smooth, pericarp very thin and fragile (less than 0.5 mm thick). Seeds 8-12 by 6-8 mm, ecarunculate.

    T h a i l a n d. Widely cultivated; collected in probably natural environments in: NORTHERN: Phrae (Silo); EASTERN: Chaiyaphum (Ban Nam Phrom).

    D i s t r i b u t i o n. Sri Lanka (type), India, through SE Asia to China, and Malesia from the Malay Peninsula to the Philippines and the Moluccas.

    E c o l o g y. In evergreen forest, over sandstone. Altitude: 600 m. Flowering and fruiting: May-August.

    V e r n a c u l a r. Hat sakhuen (หัสคืน), salot (สลอด) (General); ba kang (บะกั้ง), ma kang (มะคัง, มะข่าง), mak thang (หมากทาง), matot (มะตอด) (Northern); mak pong, mak-yong (หมากยอง) (Shan-Mae Hong Son); luk phlan sattru (ลูกผลาญศัตรู), mak lot (หมากหลอด), salot ton (สลอดต้น) (Central); Croton oil plant (English).

    U s e s. Widely cultivated as ornamental tree and for medicinal purposes. The dried leaves are crushed and used medicinally as purgative, and are mentioned as poultice for snake bites. Because of the toxicity many former uses of, e.g., wood and root in human and veterinary medicine have been abandoned. The seeds are very poisonous (2-3 seeds are lethal) and used for stupefying fish in some parts of Malesia, but also used as a drastic hydragogue purgative for man. The seed oil (Croton oil) is irritant and causes dermatitis, but diluted it can be externally applied as counterirritant for various skin affections, and rubbed on the skin it acts as a rubefacient. It has been used for outdoor illumination (the fumes are irritant). A seed extract can de used as insecticide. Cultivation is possible on very poor soil and has been tried in former times in, e.g., Sri Lanka.

    N o t e. The plants formerly separated as C. birmanicus (= C. himalaicus) differ slightly in a more distinct pubescence and usually stalked glands at the leaf base. The differences are not clearcut, and probably these taxa should be united. This had already been suspected by Airy Shaw (loc. cit.). It should be noted that in Malesia all plants confirm with the typical C. tiglium.

 

30. Croton wallichii Mll.Arg., Linnaea 34: 118. 1865 & in DC., Prodr. 15, 2: 623. 1866; Kurz, Forest Fl. Burma 2: 373. 1877; Gagnep in Lecomte, Fl. Indo-Chine 5: 282. 1925; Airy Shaw, Kew Bull. 26: 251. 1972; Chakrab. & N.P.Balakr., Bull. Bot. Surv. India 34: 75, fig. 14. 1997 (1992); Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 223. 2005.

 

Tree to 15 m tall, dbh 16 cm; bark thin, grey to light brown, finely pustular to smooth; young parts distinctly pubescent; deciduous, often flowering when leafless or with imature leaves. Indumentum consisting of stellate-dendritic hairs, cream-brown, often porrect, 0.2-0.4 mm in diam., with c. 10-15 free radii. Stipules 1.25-1.5 mm long, pubescent. Leaves alternate to crowded; petiole 1.3-3.0 cm long, scarcely to distinctly but not densely pubescent; blade (elliptic-)obovate, sometimes slightly constricted near the base, 12-19 by 5-10 cm, index 2.0-3.3, chartaceous, base acute with very base rounded to subcordate, margin serrate (teeth 3-5(-10) mm apart), apex acuminate, brighter below, glabrous above, sparsely to distinctly but not densely pubescent below; basal glands sessile, slightly prominent, c. 1 mm in diam., sometimes elongate, at least partly situated on the abaxial blade touching the midrib; side veins 10-14 pairs, not triplinerved, tertiary veinlets visible. Inflorescences erect, light green, collected with weak but not stiff erect buds, 6.5-12 cm long, usually several grouped together on leafless branches or with older leaves, but also from old leaf scars and then lateral-axillary, with numerous densely pubescent bud scales c. 2-5 mm long at base, often with 4-8 pistillate flowers, distinctly proterogynous, without bisexual bracts; densely pubescent on all parts, slightly glabrescent on most parts; bracts 1(-2) mm long, eglandular, persistent. Staminate flowers densely pubescent outside; pedicel 2.5-3.5 mm long; sepals and petals both 2.5 by 1.25 mm and both distinctly pubescent; stamens c. 10. Pistillate flowers slightly pubescent outside; pedicel (3-)4-6 mm long (9-10 mm in fruit); sepals 2-3 by 1.5 mm, nearly as long as the ovary; petals 1 mm long, filiform, glabrous; stigmas 3-4 mm long, free at base, bifid for more then half length. Fruits 5 mm long, smooth, scatteredly pubescent, sulcate. Seeds 4.5 by 4 mm, ?ecarunculate.

    T h a i l a n d. SOUTH-WESTERN: Kanchanaburi (E. of Sangkhla, Thung Yai Naresuan); PENINSULAR: Chumphon (W. of Chumphon), Ranong (Kapoe), Phangnga (Songphinong waterfalls), Surat Thani (Yan Yao), Trang (Ko Khao).

    D i s t r i b u t i o n. Burma (type), Thailand, Malay Peninsula (excl. Singapore).

    E c o l o g y. In disturbed, fire-prone forest, bamboo-rich mixed deciduous forest, on limestone. Altitude: 10-700 m. Flowering and fruiting: January-May.

    V e r n a c u l a r. Kao-o-wa (กวาโอะวะ), kao-wa (กวาวะ) (Karen-Kanchanaburi) (Southwestern); plao (เปล้า), plao na (เปล้านา) (Peninsular).

 

31. Croton sp. 1: Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 224. 2005 ?Croton joufra Roxb., Fl. Ind. ed. 1832, 3: 685. 1832; Mll.Arg. in DC., Prodr. 15, 2: 519. 1866; Kurz, Forest Fl. Burma 2: 373. 1877; Hook.f, Fl. Brit. India 5: 387. 1887; Gagnep in Lecomte, Fl. Indo-Chine 5: 280. 1925; Croizat, J. Arnold Arbor. 23: 45. 1942; Airy Shaw, Kew Bull. 26: 247. 1972.  ?Croton caryocarpus Croizat, J. Arnold Arbor. 23: 44. 1942; P.H. H, Cyco Vitnam 2, 1: 294, fig. 4463. 1992

 

Tree to 10 m tall; bark pale gray; young branchlets densely pubescent, glabrescent. Indumentum consisting of stellate, pale creamish-grey hairs, mostly flat, 0.2-0.4 mm in diam., with c. 20-30 free radii. Stipules c. 4 mm long, pubescent. Leaves alternate-crowded; petiole 1.5-3 cm long, densely pubescent, not glabrescent; blade elliptic (to slightly obovate), 16-21 by 5.5-6.5(-8.5) cm, index (2.2-)2.8-3.8, chartaceous, base acute (-obtuse-rounded), margin distinctly serrate (teeth 3-6 mm apart), apex acute-subacuminate, only slightly brighter below, glabrous above, with scattered hairs (in particular on midrib) below, hardly glabrescent; basal glands as sessile, flat to slightly elevated, c. 0.6 mm large, lateral on the midrib base, marginal glands absent; side veins 16-18 pairs, not triplinerved. Inflorescences yellowish-green (anthers yellow), often several in an apical whorl (sometimes leafless branches flowering), 8-15(-30) cm long, with 2-10 pistillate flowers, without bisexual bracts; densely pubescent throughout and not glabrescent; bracts c. 1-1.5 mm long, stiff, eglandular, not caducous. Staminate flowers densely pubescent; pedicel 2-3 mm long; sepals c. 2 by 1 mm; petals slightly narrower, distinctly pubescent throughout; stamens c. 10. Pistillate flowers densely pubescent throughout; pedicel 3-4.5 mm long; sepals 2 by 1.25 mm, slightly shorter than the ovar; petals absent; ovary 2-2.5 mm long; stigmas 2-2.5 mm long, free, nearly completely bifid. Fruits and seeds unknown.

    T h a i l a n d. NORTHERN: Chiang Mai (Doi Chieng Dao, Samong), Tak (Mae Moi); NORTH-EASTERN: Phetchabun (Thung Salaeng Luang), Loei (Phu Ruea).

    D i s t r i b u t i o n. Laos.

    E c o l o g y. In forest, further details not reported. Altitude: 500-1,400 m. Flowering: December-March.

    N o t e. This species is represented by Chantaranothai et al. 1015, 1016, Chayam. et al. 1661, Kerr 2917, Nanakorn 1077, and probably also Koyama et al. T-31902 and Konta et al. 4275. It differs in the combination of stellate hairs, serrate leaves and densely pubescent inflorescences from the other species reported for Thailand, although it superficially resembles C. roxburghii. It occurs also in Laos (Poilane 20117). It is similar to C. caryocarpus, which is a possible synonym of C. joufra, and occurs in Bangladesh, Burma, and Indo-China, and could therefore to be expected in Thailand. Diagnostic for C. caryocarpus are the remarkably large fruits over 20 mm in diam., yellowish-cream hairs, and indistinctly serrate to subentire leaves that dry in a very characteristic, yellow-green-brown colour. The Thai plants have grey-creamish hairs and very distinctly serrate leaves, and fruits are needed to assure the identity. If not C. caryocarpus/joufra, the Thai plants could represent an undescribed species.

 

Excluded names

 

Croton laccifer L., Sp. Pl.: 1005. 1753; Airy Shaw, Kew Bull. 26: 248. 1972; Chakrabarty & Balakrishnan, Bull. Bot. Surv. India 26: 200. 1984 (under C. aromaticus L.); Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 225. 2005.

    See under C. caudatus.

 

Croton leiophyllus Mll.Arg., Linnaea 34: 103. 1865 & in DC., Prodr. 15, 2: 573. 1866; Airy Shaw, Kew Bull. 26: 248. 1972; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 226. 2005.

    See under C. phuquocensis.

 

Croton santisukii Airy Shaw, Kew Bull. 35: 392. 1980; Esser in Chayam. & Welzen, Fl. Thailand 8, 1: 226. 2005.

 

Treelet to 10 m tall; younger parts densely silvery-brownish pubescent. Indumentum consisting of lepidote hairs, hyaline with a small brownish center (on leaves, appearing silvery) or brownish throughout (partly on leaves, in particular veins, dense on floral parts), flat, 0.2-0.4 mm in diam., with c. 25-30 largely to completely fused radii. Stipules 1 mm long, pubescent. Leaves alternate; petiole 4-5.5 cm long, densely pubescent; blade ovate-elliptic, 14-16 by 7-10 cm, index 1.6-2.0, chartaceous to subcoriaceous, base obtuse to rounded and slightly peltate, margin subentire, apex acuminate, soon glabrous above, completely and densely silvery-pubescent below without visible surface, with scattered darker hairs visible as brownish dots; basal glands laminar-submarginal in a row on the blade below, each gland 0.75-1 mm in diam., flat; venation distinctly darker (by brownish hairs) below, side veins 6-7 pairs below the apex, slightly triplinerved, tertiary veinlets visible. Inflorescences only known in bud with already imature fruits, solitary, c. 14 cm long, with c. 8 pistillate flowers, without bisexual bracts; densely brownish -pubescent throughout; bracts 2-2.5 mm long, eglandular, persistent. Staminate flowers densely pubescent throughout only known in early bud, then subsessile, with c. 50-60 stamens, receptacle glabrous. Pistillate flowers only known as imature fruits, then densely pubescent throughout; pedicel 17 mm long; sepals 3 by 1.5 mm, free; petals not seen; ovary smooth; stigmas unknwown. Fruits 17-20 mm long when imature, densely brownish pubescent. Seeds unknown.

    T h a i l a n d. SOUTH-WESTERN: Prachuap Khiri Khan (Bang Saphan, type: Beusekom & Santisuk 2797, holotype AAU, isotypes BKF, L, P).

    D i s t r i b u t i o n. Endemic?

    E c o l o g y. In secondary forest with evergreen patches Altitude low. Immature flowers and fruits in February.

    V e r n a c u l a r. Plao santisuk (เปล้าสันติสุข) (Southwestern).

    N o t e. A distinct species, but certainly not a Croton. Unusual leaf glands and peltate leaf base, high stamen number, long fruiting pedicels are unusual characters. Unfortunately still known from a single collection only without mature flowers or fruits.