Flora of Thailand

 

Euphorbiaceae

 

Key to the Species of Hancea, Macaranga, and Mallotus of Thailand

 

Peter C. van Welzen & Stuart J. Davies

 

This chapter is added, because usually in floras one first has to identify the genus and then in a next key the species. However, the distinction betweeen the genera Hancea, Macaranga, and Mallotus is difficult (number of locules in the stamens and the dehiscence of the fruits). Most people recognize a plant as belonging to this group, but they do not know the exact genus name. Therefore, this key makes identification up to genus level superfluous.

This page differs from the Flora of Thailand edition, Trewia is now part of Mallotus, and a part of Mallotus has become Hancea.

 

1a.

All or most leaves alternate (sometimes opposite beneath inflorescence; inflorescence always in the axil of a leaf)

2

1b.

All leaves opposite (in some species opposite leaf stipule-like and caducous, then inflorescence opposite to leaf)

45

2a.

Leaves 1 cm or more peltate

3

2b.

Leaves less than 1 cm peltate

22

3a.

Twigs hollow, ant-inhabited

4

3b.

Twigs solid, not ant-inhabited

8

4a.

Twigs densely whitish glaucous

5

4b.

Twigs not glaucous

7

5a.

Leaves trilobed with the central lobe narrowly ovate, substantially longer and wider than the lateral lobes. Fruits 45 locular

6. Macaranga griffithiana

5b.

Leaves trilobed with the lobes broadly ovate, more or less equal in size and shape. Fruits 2 or 3 locular

6

6a.

Lower surface of leaf blade intensely white. Stipules triangular. Fruits 3-locular. Dry land

10. Macaranga hypoleuca

6b.

Lower surface of leaf blade not white. Stipules broadly rounded. Fruits 2-locular. Swamps

18. Macaranga pruinosa

7a.

Mature leaves broadly ovate, trilobed. Young leaves reddish brown furfuraceous. Staminate bracteoles rounded to broadly acute, rusty furfuraceous

2. Macaranga bancana

7b.

Mature leaves narrowly ovate, usually entire, or with short lateral cusps. Young leaves green, glabrous. Staminate bracteoles caudate, glabrous

9. Macaranga hullettii

8a.

Leaves and twigs massive. Leaf blades usually at least 40 cm long. Stipules large, usually longer than 20 mm

9

8b.

Leaf blades shorter than 35 cm, rarely more. Stipules shorter than 15 mm

10

9a.

Twigs with silvery, harsh persistent hairs. Petioles D-shaped in section. Upper leaf surface without prominent extrafloral nectaries. Peninsular

5. Macaranga gigantea

9b.

Twigs with soft, light-brown caducous hairs. Petioles round in section. Upper leaf surface with prominent extrafloral nectaries near the leaf apex. Absent from Peninsular

19. Macaranga siamensis

10a.

Leaves trilobed, lobes more than 5 cm long

22. Macaranga triloba

10b.

Leaves not lobed (or sometimes lobed, but then lobes up to 5 cm long)

11

11a.

Upper leaf blade surface without (basal) extrafloral nectaries

12

11b.

Upper leaf blade surface with extrafloral nectaries, at least close to insertion with petiole

14

12a.

Leaves, twigs, inflorescence axes and bracteoles glabrous

4. Macaranga diepenhorstii

12b.

With scattered to very dense hairs on most parts

13

13a.

Leaf blades thick, often drying chocolate brown, margin recurved. Staminate bracteoles entire. Fruits smooth, without spines

16. Macaranga pachyphylla

13b.

Leaves thinly papery, drying pale brown, margin not recurved. Staminate bracteoles deeply irregularly dissected. Fruits with long tentacle-like spines

20. Macaranga tanarius

14a.

Lower leaf blade surface and branches distinctly hairy to the touch

15

14b.

Lower leaf blade surface glabrescent (sometimes hairy to the touch), branches not distinctly hairy

17

15a.

Indumentum floccose (among hairs are strap-like enations densely covered with hairs, providing an irregular indumentum layer)

2. Mallotus barbatus

15b.

Indumentum in a regular layer, not floccose

16

16a.

Glandular scales absent from upper leaf surface; apical extrafloral nectaries usually absent. Plants not smelling of fenugreek. Fruits densely set with c. 400 c. 7 mm long spines. Stamens 70-80

21. Mallotus metcalfianus

16b.

Glandular scales on upper leaf surface, mainly near insertion; apical extrafloral nectaries usually present. Plants (usually) smelling of fenugreek. Fruits set with less than 100, less than 5 mm long spines. Stamens 40-50

36. Mallotus thorelii

17a.

Margin of leaf blade entire. Stellate hairs absent

18

17b.

Margin of leaf blades serrate or with a few short teeth. Stellate hairs present

21

18a.

Leaves deltate, c. 1 cm peltate. Leaf base strongly truncate to square. Staminate bracteoles indistinct, smaller than the flower clusters. Extrafloral nectaries aggregated at petiole insertion

19

18b.

Leaves ovate, >2 cm peltate. Leaf base rounded, not truncate. Staminate bracteoles prominent, larger than the flower clusters. Extrafloral nectaries near leaf base and/or apex

20

19a.

Stipules elliptic, c. 3 by 1 mm. Staminate and pistillate bracts tiny, inconspicuous, 1 mm, rounded, bracteoles similar but smaller. Widespread, common

3. Macaranga denticulata

19b.

Stipules oblong-acute, c. 6 by 2 mm. Pistillate bracts obovate, to 11 by 2 mm, crenate, with numerous conspicuous marginal glands, bracteoles similar but smaller. Staminate unknown. Peninsular, once collected

15. Macaranga neodenticulata

20a.

Leaf blades nearly always with a few conspicuous elongate extrafloral nectaries on main nerves somewhat distant from petiole insertion. Staminate inflorescence branches usually strongly zigzag. Staminate bracteoles spoon-like with 1-2 subapical glands

11. Macaranga indica

20b.

Leaf blades with round extrafloral nectaries near the basal and apical leaf margins. Staminate inflorescence branches not strongly zigzag. Staminate bracteoles ovate, apex rounded to broadly acute

17. Macaranga peltata

21a.

Leaf blades about as long as wide (length/width ratio 1.31.4). Plant distinctly smelling of fenugreek. Pistillate sepals recurved below ovary, not enclosing ovary and style, persistent

8. Mallotus floribundus

21b.

Leaf blades much longer than wide (length/width ratio 1.83.8). Plant usually not or slightly smelling of fenugreek. Pistillate calyx urceolate around ovary and style, caducous

28. Mallotus peltatus

22a.

Stellate hairs absent (or occasionally a single one: Mallotus subpeltatus), only simple hairs

23

22b.

Stellate hairs present (next to simple ones)

30

23a.

Inflorescences up to 1 cm long. Stamens 200-250. Leaves subpeltate, margin entire. Ovary and fruit 3-locular. Fruits with spines

4. Hancea subpeltata

23b.

Inflorescences much longer. Stamens less than 20. Leaves not peltate to subpeltate, margin entire to dentate. Ovary and fruit 2-locular. Fruits with or without spines

24

24a.

Twigs hollow, ant-inhabited. Leaf blades with 3 equal lobes

8. Macaranga hosei

24b.

Twigs solid, not ant-inhabited. Leaf blades either entire or if trilobed with central lobe much larger than laterals

25

25a.

Stipules and bud scales finely pointed, erect and clustered at the twig apex. Primary forest

26

25b.

Stipules triangular or elliptic, sometimes recurved, not crowded with bud scales at twig apex. Secondary forest

27

26a.

Stipules and bud scales chocolate (dark) brown, with sparse spreading white whiskers. Pistillate spikes with terminal flowers and fruits. Staminate spikes threadlike, flower clusters 11.5 mm across, never malformed

1. Macaranga andamanica

26b.

Stipules and bud scales chestnut (light) brown, glabrous. Pistillate flowers and fruits spaced along top of spike. Staminate spikes with 1 mm axis, flower clusters 34 mm across, often malformed as witches' brooms (many, tightly packed flowers)

14. Macaranga lowii

27a.

Twigs, petioles and especially inflorescence axes with long spreading silvery-white hairs. Staminate bracteoles minute, often absent. Fruits subtended by large opposite leaf-like bracts

12. Macaranga kurzii

27b.

Twigs, petioles and inflorescence axes often tomentose or shortly pubescent, but without long spreading silvery hairs. Staminate bracteoles prominent and larger than the flower clusters. Fruits subtended by small caducous bracts

28

28a.

Leaves densely coarsely pubescent on upper surface; margin coarsely toothed. Fruits covered in long thin spines. Bushy tree with sprawling limbs

21. Macaranga trichocarpa

28b.

Leaves glabrous above; margins entire. Fruits without spines. Small erect trees

29

29a.

Stipules elliptic including a long narrow tip 10 by 1.5 mm, erect. Bracteoles ovate to 10 by 6 mm with distant long, linear blunt teeth

7. Macaranga heynei

29b.

Stipules  triangular, c. 10 by 4 mm, acuminate, recurved. Bracteoles of ovate outline 8 mm long, deeply finely dissected (laciniate), sometimes with no central lamina

13. Macaranga laciniata

30a.

Leaf blades ovate, length/width ratio up to 1.8 (blades about as long as broad to less than 2x as long as broad), with 2 lobes or not (measure!, because some species seem to have long blades)

31

30b.

Leaf blades ovate to obovate, length/width ratio 1.7 (elliptic) or more, lobes absent

37

31a.

Upper surface of leaf blades with orangish glandular scales, especially near insertion (use hand lens or microscope)

36. Mallotus thorelii

31b.

Upper surface of leaf blades without glandular scales (only present on lower surface)

32

32a.

Leaf blades below (sub)glabrous to glabrescent, at most few hairs on veins

9. Mallotus garrettii

32b.

Leaf blades below densely hairy: dense indumentum on veins (and often on epidermis, then leaves whitish beneath)

33

33a.

Scandent shrub to woody climber. Lower leaf blade surface not whitish (hairs only on venation, epidermis visible). Inflorescences mainly axillary, not branching. Stamens c. 50. Ovary and fruit smooth, no spines, 2-locular

32. Mallotus repandus

33b.

Shrubs to trees. Lower leaf blade surface whitish (epidermis also densely hairy). Inflorescences mainly terminal, branching. Stamens 45 to more. Ovary and fruit with spines, (2)3-4(5)-locular

34

34a.

Leaves usually broadest above lower third to middle, base (narrowly emarginate to round to) usually cuneate with two large extrafloral nectaries, (1-3) by (1-)2 mm; margin often with 1 or 2 lobes, up to 3.5 cm long. Ovary and fruits sparsely set with c. 30 hard spines

27. Mallotus paniculatus

34b.

Leaves broadest below lower third, base emarginate to rounded, with 2 to more extrafloral nectaries, 1-2.5 by 0.3-1.3 mm (sometimes confluent and then seemingly much larger); margin without or with a single extremely short lobe (less than 1 cm: M. tetracoccus). Ovary and fruits densely set with 100 or more hard or soft spines

35

35a.

Peltate part of leaf blade usually folded upwards; lower surface usually with pocket domatia full with hair tufts. Fruit (and ovary) covered with one continuous layer of soft spines, individual spines nor fruit wall visible. P

20. Mallotus macrostachyus

35b.

Peltate part of leaf blade absent or flat; lower surface without domatia. Fruits (and ovary) covered with far less spines, individual spines (and, in older fruits, fruit wall) visible

36

36a.

Upper surface of leaf blade usually without or 1 or 2 apical extrafloral nectaries; glandular scales on lower surface not visible. Staminate flowers with 3 sepals; stamens 70-80. Fruit set with c. 400 soft spines, up to 7 mm long

21. Mallotus metcalfianus

36b.

Upper surface of leaf blade usually with (0 to) few to many apical extrafloral nectaries; glandular scales on lower surface visible (microscope!, sometimes rare). Staminate flowers with (2)4-5(6) sepals; stamens 45-65. Fruit set with c. 100 stiff spines, up to 3 mm long

35. Mallotus tetracoccus

37a.

Lower leaf surface whitish because of dense hairs on venation and epidermis. Ovary and fruits without spines

38

37b.

Lower leaf surface (sub)glabrous to densely hairy on venation only (not whitish, epidermis visible; use microscope). Ovary and fruits armed or not, with or without spines

40

38a.

Glandular scales yellowish. Stipules 3.5-5.5 mm long. SW (Sam Roi Yot)

26. Mallotus pallidus

38b.

Glandular scales red or greenish (orange when fresh). Stipules 0.5-1.5 mm long. All over Thailand

39

39a.

Glandular scales greenish when dry (orange when fresh) , only visible on fruits, scarcely visible on lower leaf surface. Fruits 11-14 by c. 11 mm, wall 2-3 mm thick. N (Kamphaeng Phet)

15. Mallotus kongkandae

39b.

Glandular scales reddish, well visible on fruits and lower leaf surface. Fruits 8-12 by 6-8 mm, wall less than 2 mm thick. All over Thailand

29. Mallotus philippensis

40a.

Leaf blades on upper surface with orangish glandular scales (hand lens or microscope), (sub)glabrous. Fruits winged or not, indehiscent or tardily (late) dehiscent 

41

40b.

Leaf blades on upper surface without glandular scales, only present on lower surface, glabrous to densely hairy. Fruits never winged, dehiscing

42

41a.

Leaf blades 9.8-27 cm long, often with hair tuft domatia in nerve axils beneath. Stamens 26-37, filaments 1.5-3 mm long. Ovary and fruit not winged, tardily dehiscent. Stipules 1.5-2.5 mm long

19. Mallotus leucodermis

41b.

Leaf blades 5.5-16 cm long, without domatia underneath. Stamens 20-25, filaments 0.5-1.5 mm long. Ovary and fruits with upward pointing wings, indehiscent. Stipules 0.7-0.9 mm long

31. Mallotus plicatus

42a.

Leaf blades ovate, widest basally or below lower third, (sub)glabrous. N

9. Mallotus garrettii

42b.

Leaf blades elliptic or obovate, widest at lower third or higher, (sub)glabrous to hairy on nerves. All over Thailand

43

43a.

Glandular scales on lower leaf blade surface few. Stamens 25-35. Ovary and fruits armed with spines

28. Mallotus peltatus

43b.

Glandular scales on lower leaf blade surface distinct. Stamens 55-70. Ovary and fruits without spines

44

44a.

Leaf blade elliptic, margin subentire with glandular teeth. SW (Kanchanaburi), P

17. Mallotus leptostachyus

44b.

Leaf blade ovate, margin entire. SW (Sam Roi Yot)

26. Mallotus pallidus

45a.

Opposite leaf reduced to stipule or orbicular / heart-shaped (different in shape from opposite leaf). Inflorescences opposite to large leaf. --- Plants rare, only in the Peninsula

46

45b.

Opposite leaves of same shape, one usually somewhat smaller. Inflorescences in axil of smaller leaf

49

46a.

Petioles less than 2 cm long

47

46b.

Petioles longer than 2 cm

48

47a.

Blade of smaller leaf orbicular / heart-shaped, 0.8-5.5 by 0.8-4.8 cm

22. Mallotus miquelianus

47b.

Blade of smaller leaf stipule-like, triangular, 4-10 by 1.5-2.5 mm

3. Hancea stipularis

48a.

Leaf blades hairy underneath

1. Hancea kingii

48b.

Leaf blades glabrous underneath

2. Hancea penangensis

49a.

Length/width ratio of leaf blades less than 1.8(-1.9) (leaf blade about as broad as long to up to 1.8-1.9 times as long as broad)

50

49b.

Length/width ratio of leaf blades more than 1.8 (leaf blades about twice to more as long as broad)

55

50a.

Leaf blades ovate, margin entire. Deciduous, flowering when young leaves appear. Fruits indehiscent drupes. Stellate hairs often very long and soft 

25. Mallotus nudiflorus

50b.

Leaf blades ovate to obovate, margin subentire to dentate. Not deciduous, flowering when in full leaf. Fruits dehiscent capsules. Stellate hairs short to long, not soft 

51

51a.

Lower leaf blade surface densely tomentose, hairs also on epidermis, epidermis not visible; glandular scales orange; margin subentire (few teeth).---Near sea

37. Mallotus tiliifolius

51b.

Lower leaf blade surface subglabrous to hairy on nerves only, epidermis visible; glandular scales yellow, orange or reddish; margin dentate

52

52a.

Leaf blade elliptic to obovate; glandular scales many on lower surface (microscope). Stipules 4-10 by 1.2-6 mm (large)

53

52b.

Leaf blade ovate (to obovate); glandular scales almost absent to few on lower surface (microscope). Stipules 1.6-5.5 by 0.51.5 mm (smaller)

54

53a.

Stipules 1.2-1.5 mm wide. Upper leaf blade surface drying brownish-greenish, basally with 2 large extrafloral nectaries, 0.5-2 by 0.5-1 mm

7. Mallotus dispar

53b.

Stipules 2-6 mm wide. Upper leaf blade surface drying greenish, basally with 2 to many small extrafloral nectaries, 0.3-0.5 by 0.3-0.5 mm

18. Mallotus leucocalyx

54a.

Lower leaf blade surface only along the very basal edge with a few glandular scales. Staminate sepals 3; stamens c. 50. Pistillate sepals 5 or 6; stigmas c. 4.2 mm long

13. Mallotus hymenophyllus

54b.

Lower leaf blade surface all over with a few glandular scales. Staminate sepals 4 or 5; stamens 25-35. Pistillate sepals 4 or 5; stigmas 1.8-2.3 mm long

30. Mallotus pierrei

55a.

Venation penninerved (basal nerves not distinctly different from others)

56

55b.

Venation palmate or triplinerved (basal nerves more distinct than others)

64

56a.

Leaf petiole 0.2-0.4 cm long

3. Mallotus brevipetiolatus

56b.

Leaf petiole 0.1-8 cm long (always leaves with petiole longer than 0.4 cm)

57

57a.

Staminate inflorescences up to 43 cm long; pistillate ones up to 28 cm

14. Mallotus khasianus

57b.

Inflorescences less than 10 cm long

58

58a.

Stipules needle-like, 3-6.2 by 0.4-0.5 mm (narrow). Upper leaf blade surface without extrafloral nectaries

12. Mallotus hispidospinosus

58b.

Stipules broader, 2-9 by 1-3 mm (broader). Upper leaf surface with extrafloral nectaries, especially basally

59

59a.

Fruits and petioles densely hairy. Lower leaf surface hairy or midrib hairy. SE, P

60

59b.

Fruits and petioles glabrous to densely hairy. Lower leaf blade surface (sub)glabrous to sparsely hairy. NE, SE, P

61

60a.

Glandular scales absent. Blade apex caudate, lower leaf surface densely hairy only on midrib P

1. Mallotus actinoneurus

60b.

Glandular scales whitish, sparsely present near base on lower leaf surface. Blade apex acuminate, lower leaf surface hairy

4. Mallotus calocarpus

61a.

Margin of leaf blade crenulate to subentire to denticulate with glandular teeth

62

61b.

Margin of leaf blade entire or with a single subapical tooth per side

63

62a.

Upper surface of leaf blade with 48 marginal extrafl oral nectaries per side. Pistillate infl orescences (staminate ones

unknown) reduced to single, terminal fl ower surrounded by bracts

 

23. Mallotus mirus

62b.

Upper surface of blade with 2 or 3 extrafl oral nectaries near base close to midrib. Infl orescences up to 6.3 cm long

33. Mallotus resinosus

63a.

Leaf margin with a single subapical tooth per side, apex acuminate, upper surface with extrafl oral nectaries in loops of nerves. Fruits smooth. NE

11. Mallotus glomerulatus

63b.

Leaf margin without teeth, apex bluntly acute, upper surface with extrafl oral nectaries on nerves except above third nerve. Fruits with spines. P

40. M. tokiae

64a.

Staminate inflorescences less than 4 cm long; pistillate inflorescences up to 4 cm long or up to 8 cm long, but then inflorescences umbelliform

65

64b.

Staminate inflorescences more than 5 cm long, pistillate ones up to 12 cm long, never umbelliform

68

65a.

Leaf blades elliptic; upper surface without extrafloral nectaries; lower surface subglabrous to somewhat hairy on venation. Staminate and pistillate inflorescences up to 2 cm long, not umbelliform. Stamens c. 25. Fruits without spines

5. Mallotus coudercii

65b.

Leaf blades ovate (to elliptic); upper surface with extrafloral nectaries, especially basally; lower surface subglabrous to densely hairy. Staminate and pistillate inflorescences up to 2-8 cm long. Stamens 20-30 (leaves hairy beneath) or 40 or 60. Fruits with or without spines

66

66a.

Lower leaf blade surface subglabrous to hairy on venation, hair tuft domatia present in all or most nerve axils. Stamens c. 60. Pistillate sepals 5-5.2 mm long; ovary spiny

10. Mallotus glabriusculus

66b.

Lower leaf blade surface densely hairy, hair tuft domatia absent or only in basal nerve axils. Stamens 20-40. Pistillate sepals 3-4 mm long; ovary spiny or smooth

67

67a.

Lower leaf blade with hair tuft domatia in basal nerve axils. Ovary and fruit smooth. Pistillate inflorescence a raceme. Stamens 20-30

24. Mallotus montanus

67b.

Lower leaf blade without hair tuft domatia. Ovary and fruit with spines. Pistillate inflorescence umbelliform. Stamens c. 40

34. Mallotus subcuneatus

68a.

Leaf blades ovate

69

68b.

Leaf blades elliptic to obovate

71

69a.

Fruits indehiscent drupes, smooth, no spines. Leaf blade margin entire

25. Mallotus nudiflorus

69b.

Fruits dehiscent capsules, with or without spines. Leaf blade margin laxly denticulate or serrulate

70

70a.

Fruits smooth, without spines. Lower leaf blade surface densely hairy with hair tuft domatia in basal nerve axils, glandular scales whitish 

24. Mallotus montanus

70b.

Fruits with spines. Lower leaf blade surface subglabrous to densely hairy on venation, hair tuft domatia absent, glandular scales yellow

30. Mallotus pierrei

71a.

Leaves drying brownish (if greenish, then nerves not yellowish)

16. Mallotus lanceolatus

71b.

Leaves drying greenish, nerves drying yellowish

72

72a.

Stipules 2-6 mm wide (4-10 mm high). Upper surface of leaf blade basally with 2-12 small (0.3-0.5 mm in diameter) extrafloral nectaries on each side along margin

18. Mallotus leucocalyx

72b.

Stipules 0.5-2 mm wide (1.6-6.3 mm high). Upper surface of leaf blade basally with 1-2 pairs of large extrafloral nectaries (0.5-2 mm in diameter), sometimes smaller additional ones along margin

73

73a.

Leaf blades distinctly obovate (to smaller ones sometimes elliptic), margin dentate, upper surface basally usually at least with 2 relative large extrafloral nectaries on basal nerves, up to 5 per leaf side, up to 1 by 0.5 mm

6. Mallotus decipiens

73b.

Leaf blades elliptic to obovate, margin denticulate, upper surface with 1 or 2 basal pairs of large extrafloral nectaries (0.5-2 mm in diameter) or 1-3 pairs of small extrafloral nectaries (up to 0.7 mm)

74

74a.

Stipules 1.2-1.5 mm wide. Bracts 3-8.2 by 2-3 mm. Extrafloral nectaries on upper blade surface large, 0.5-2 mm in diameter. P

7. Mallotus dispar

74b.

Stipules 0.5-1.1 mm wide. Bracts 1-4 by 0.6-0.7 mm. Extrafloral nectaries on upper blade surface small, up to 0.7 mm in diameter. All over Thailand

30. Mallotus pierrei