Begonia, Linnaeus, 1753

Hughes, Mark, Girmansyah, Deden & Ardi, Wisnu Handoyo, 2015, Further discoveries in the ever-expanding genus Begonia (Begoniaceae): fifteen new species from Sumatra, European Journal of Taxonomy 167, pp. 1-40 : 3-6

Genus Begonia L. ( Linnaeus 1753)

The key covers 58 of the 63 currently accepted names in Begonia for Sumatra. Six names are excluded, of which 5 are those described by Jack ( Jack 1822) ( B. caespitosa Jack , B. geniculata Jack , B. orbiculata Jack and B. pilosa Jack ) for which the type material has been lost and no other specimens are known ( Hughes & Girmansyah 2011b), and one described by Miquel [ B. hasskarliana (Miq.) A.DC. (de Candolle 1864; basionym Miquel 1856)] for which no specimens are known. In all cases the original descriptions for those species do not provide enough detail to enable confident placement in the key. Some of the couplets key out to more than one name, as there are several names which appear refer to the same species, although they have not been formally synonymised to date.

Key to the Begonia of Sumatra

1. Plant without an erect main stem, petioles and peduncles arising from a rhizome (§ Reichenheimia ) ........................................................................................................................................................ 5

– Plant with some parts of the stem erect, with at least some internodes> 2 cm apart .................... 2

2. Plants rhizomatous at the base, erect stem portion repent against tree trunks or rocks, styles 2, fruit 2-locular with one enlarged wing (§ Platycentrum ) ..................................................................... 27

– Plants rhizomatous or not at the base, erect stem portion self-supporting, styles 3, fruit 3-locular with equal or subequal wings or wings absent ................................................................................ 3

3. Fruits fleshy berries without wings (ridges sometimes present); anthers with an extended connective, dehiscing through lateral slits (§ Sphenanthera ) ...................................................... 30

– Fruits dry dehiscent, winged; anthers without an extended connective, dehiscing through slits on one face of the anther ...................................................................................................................... 4

4. Plants erect, cane like, stems glabrous, inflorescences cymose, ovaries glabrous (§ Petermannia and cane species unplaced to section) ........................................................................................... 33

– Plants spreading, stems hairy, inflorescences fasciculate, ovaries with short hairs (§ Bracteibegonia) ...................................................................................................................................................... 44

5. Leaves distinctly peltate ................................................................................................................. 6

– Leaves basifixed or barely peltate ................................................................................................. 10

6. Leaves sparsely pilose above ........................................... B. sudjanae C.-A.Jansson ( Jansson 1963)

– Leaves glabrous above ................................................................................................................... 7

7. Petioles densely pilose .............................................................. B. halabanensis M.Hughes sp. nov.

– Petioles glabrous ............................................................................................................................ 8

8. Petioles triangular in cross-section, lamina rugose ................. B. goegoensis N.E.Br. ( Brown 1882)

– Petioles terete in cross-section, lamina not rugose .......................................................................... 9

9. Leaves purple in the centre, rhizome creeping, fruits recurved on a stiff pedicel ............................... .................................................................................................. B. karangputihensis Girm. sp. nov.

– Leaves uniform green, rhizome erect, fruits dangling on a thin pedicel ............................................. .............................................................................................................. B. kudoensis Girm. sp. nov.

10. Petiole apex with several fleshy red bristles .................................................................................. 11

– Petiole apex without bristles ......................................................................................................... 13

11. Leaves with acute lobes ................................................................................................................ 12

– Leaves without lobes .................................................... B. korthalsiana Miq. ex M.Hughes sp. nov.

12. Leaf base cuneate .............................................................................. B. fluvialis M.Hughes sp. nov.

– Leaf base cordate ............................................................................... B. sublobata Jack ( Jack 1822)

13. Leaf base cuneate ......................................................................................................................... 14

– Leaf base cordate .......................................................................................................................... 15

14. Leaf lamina c. 1 cm wide, subsymmetric .................................... B. lilliputana M.Hughes sp. nov.

– Leaf lamina 1.4–3 cm wide, asymmetric ................................... B. inversa Irmsch. ( Irmscher 1954)

15. Leaf lamina densely pilose above .......................................... B. puspitae Ardi ( Hughes et al. 2009)

– Leaf lamina glabrous above .......................................................................................................... 16

16. Petiole densely hairy, with erect hairs c. 3–9 mm long ................................................................ 17

– Petiole glabrous, sparsely hairy, or with appressed hairs .............................................................. 20

17. Leaf lamina broadly ovate, basal lobes not overlapping ............. B. trichopoda Miq. ( Miquel 1856)

– Leaf lamina suborbicular, basal lobes overlapping ....................................................................... 18

18. Leaf lamina with 3–5 short acute points ................................... B. kemumuensis M.Hughes sp. nov.

– Leaf lamina entire or denticulate .................................................................................................. 19

19. Petioles and peduncles 30–60 cm long, inflorescence with c. 100 flowers ........................................ ...................................................... B. sychnantha L.B.Sm. & Wassh. ( Smith & Wasshausen 1984)

– Petioles and peduncles <30 cm long, inflorescence with c. 50 flowers ............................................ .......................................................................................................... B. raoensis M.Hughes sp. nov.

20. Leaf apex with a distinct acumen at least 1 cm long ..................................................................... 21

– Leaf apex rounded, obtuse or with an acumen <1 cm long ........................................................... 22

21. Leaf lamina with 3–5 short acute points ............................................................................................ ............................................. B. longipedunculata Golding & Kareg. ( Smith & Wasshausen 1984)

– Leaf lamina entire or denticulate ....................................................................................................... ......................................... B. stictopoda (Miq.) A.DC. (de Candolle 1864; basionym Miquel 1856)

22. Tepals on male flowers with bristles at the base ................................................................................. ............................................................................ B. pasamanensis M.Hughes ( Hughes et al. 2009)

– Tepals on male flowers glabrous ................................................................................................... 23

23. Stipules glabrous or with a few hairs on the keel .......................................................................... 24

– Stipules densely hairy ................................................................................................................... 25 24. Leaf lamina suborbicular,> 6 cm in diameter ...................................... B. rajah Ridl. ( Ridley 1894)

– Leaf lamina ovate, <4.5 cm long ......................................... B. ionophylla Irmsch. ( Irmscher 1913)

25. Leaf lamina ovate .............................................................. B. droopiae Ardi ( Ardi & Hughes 2010)

– Leaf lamina suborbicular .............................................................................................................. 26

26. Leaf lamina 5–9.5 × 4–8 cm, glossy green above ............................... B. simolapensis Ardi sp. nov.

– Leaf lamina 2.7–4.5 × 2.6–3.7 cm, matt olive green above ........................ B. olivacea Ardi sp. nov.

27. Leaves hairy above ....................................................................................................................... 28

– Leaves glabrous above ................................................................................................................. 29

28. Leaf lamina not variegated, with acute lobes, with bristly hairs ....................................................... B. areolata Miq. ( Miquel 1855) / B. beccariana Ridl. ( Ridley 1923) / B. bifolia Ridl. ( Ridley 1917)

– Leaf lamina variegated, not lobed, with soft hairs .......... B. tuberculosa Girm. ( Hughes et al. 2009)

29. Leaf lamina lobed, female flowers with 6 tepals .......................... B. leuserensis M.Hughes sp. nov.

– Leaf lamina not lobed, female flowers with 5 tepals .................................................................... ......................................................................... B. altissima Ridl. ( Ridley 1917) / B. laevis Ridl. ( Ridley 1917) / B. teysmanniana (Miq.) Tebbitt ( Tebbitt & Dickson 2000; basionym Miquel 1856)

30. Leaf lamina with 5–7 broad pointed lobes ............................... B. multangula Blume ( Blume 1827)

– Leaf lamina not lobed ................................................................................................................... 31

31. Leaf lamina ovate ......................................................................................................................... 32

– Leaf lamina lanceolate ............................................................... B. longifolia Blume ( Blume 1827)

32. Plant with white hairs, fruits borne apically in pairs ....................... B. scottii Tebbitt ( Tebbitt 2005)

– Plant with pink hairs, fruits borne basally in a cluster of 10–20 ....... B. pseudoscottii Girm. sp. nov.

33. Leaf lamina with acute lobes ............................................ B. laruei M.Hughes ( Hughes et al. 2009)

– Leaf lamina without lobes ............................................................................................................ 34

34. Petioles tuberculose-tomentose ......................................... B. padangensis Irmsch. ( Irmscher 1954)

– Petioles glabrous .......................................................................................................................... 35

35. Leaf lamina with rows of bristles between the veins on the upper surface ......................................... ........................................... B. vuijckii Koord. ( Koorders 1912) / B. tenericaulis Ridl. ( Ridley 1925)

– Leaf lamina glabrous above .......................................................................................................... 36

36. Inflorescences arising at the base of a shortened petiole, appearing to have a subtending leaf, female flowers distal ..................................................................................................................... 37

– Inflorescences without a subtending leaf on a shortened petiole, female flowers basal ................ 38

37. Leaf margin dentate-denticulate, flowers white, 1300–1800(–2300) metres altitude ........................ .............................................................................................. B. divaricata Irmsch. ( Irmscher 1954)

– Leaf margin denticulate, flowers pink, 30–600(–1200) metres altitude ............................................ ............................................................... B. gracilicyma Irmsch. ex M.Hughes ( Hughes et al. 2009)

38. Lamina elongate-lanceolate, apex long acuminate, margin entire to shallowly undulate .................. ............................................................................................................. B. harauensis Girm. sp. nov.

– lamina ovate or lanceolate, apex acuminate or shortly acuminate, margin dentate to shallowly dentate .......................................................................................................................................... 39

39. Fruit pedicel dangling,> 2 cm long ............................................................................................... 40

– Fruit pedicel stiff, <2 cm long ...................................................................................................... 41

40. Fruit bell-shaped, leaves 6–15 cm wide ............................................................................................ .............................................. B. atricha Miq. (A.DC.) (de Candolle 1864; basionym Miquel 1856)

– Fruit suborbicular, leaves <6 cm wide .......................................... B. repanda Blume ( Blume 1827)

41. Fruits borne in clusters of up to 5 pairs, fruit wings <3 mm wide ...................................................... ................................................................................ B. multijugata M.Hughes ( Hughes et al. 2009)

– Fruits borne singly or in pairs, fruit wings> 3 mm wide ............................................................... 42

42. Locule distinctly long and narrow, c. 4 × 0.5 cm ......... B. dolichocarpa Girm. ( Girmansyah 2012)

– Locule not distinctly long and narrow, less than 2 cm long ........................................................... 43

43. Male flowers with 4 tepals, female flowers with 5 tepals, leaves ovate .............................................. ............................................................................................... B. holttumii Irmsch. ( Irmscher 1913)

– Male flowers with 2 tepals, female flowers with 3 tepals, leaves oblong-lanceolate ......................... ........................................................................................................... B. racemosa Jack ( Jack 1822)

44. Stipules broadly ovate, leafy, staying green near the apex of the plant ......................................... 45

– Stipules lanceolate, rapidly drying papery .................................................................................... 46

45. Leaves sinuate ........................................................................ B. aberrans Irmsch. ( Irmscher 1954)

– Leaves sinuate-dentate .......................................... B. horsfieldii Miq. ex A.DC. (de Candolle 1864)

46. Leaves dentate-denticulate, margin hairy ..................................................................................... 47

– Leaves entire to sinuate-dentate, margin glabrous ........................................................................ 48

47. Leaves c. 8 × 4 cm, with dense soft white hairs above ..................... B. bracteata Jack ( Jack 1822)

– Leaves 2.5–5.5 × 1.2–2.5 cm, with evenly spaced bristles above between the veins ....................... ......................................................................................................... B. jackiana M.Hughes sp. nov.

48. Plants less than 20 cm tall, becoming repent and rooting at the lower nodes, often with less than 5 leaves ............................................................................................................................................ 49

– Plants taller than 20 cm, not repent, usually with more than 5 leaves ........................................... 51

49. Leaves ovate, margin entire ......................................... B. triginticollium Girm. ( Girmansyah 2012)

– Leaves ovate-oblong, margin sinuate-dentate or dentate-crenate ................................................. 50

50. Male flowers with 2 tepals, stem, petioles and leaf underside with bright red hairs ......................... ................................................................................................. B. beludruvenea M.Hughes sp. nov.

– Male flowers with 4 tepals, stem, petioles and leaf underside with white hairs .................................. .................................................................................. B. verecunda M.Hughes ( Hughes et al. 2009)

51. Leaf lamina ovate-laceolate, base subcordate, fruit cuneate at base, male flowers with 4 tepals ....... ........................................................................................................ B. lepidella Ridl. ( Ridley 1917)

– Leaf lamina elongate-lanceolate, base narrowly cuneate, fruit rounded at base, male flowers with 2 tepals ............................................................................................... B. flexula Ridl. ( Ridley 1923)