Begonia (sect. Platycentrum) thomsonii : de Candolle 1864
Creators: name: Camfield, Rebecca
name: Hughes, Mark
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Cucurbitales
Begoniaceae
Begonia
Begonia thomsonii

description: Begonia thomsonii A.DC. [sect. Platycentrum]
Fig. 60
Annales des Sciences Naturelles; Botanique, Sér. 4, 11:135 (de Candolle 1859).
– Type: India, Meghalaya, Khasia, Hooker & Thomson 16 (lecto-: K000761433, here designated; isolecto-: B100365194).
Begonia barbata Wall. ex A.DC., Prodromus Systematis Naturalis Regni Vegetabilis 15 (1): 348 (de Candolle 1864), syn. nov.
– Type: India, Meghalaya, Sillet Hills, 1832, Silva & Bruce s.n., Wallich Cat. No. 3679A (lecto-: K-W, barcode K000542893, here designated; isolecto-: B n.v., BM001122246, G-DC).
Begonia barbata Wall., A numerical list of dried specimens of plants in the East India Company’s Museum: 129, 3679 (Wallich 1831), nom. nud.
Citations in other publications
As B. thomsonii: de Candolle (1864: 349), Clarke (1879: 647), Clarke (1881: 119), Kanjilal (1938: 334), Fischer (1938: 98), Deb (1961: 285), Chauhan (2000: 427), Kumar (2002: 653), Kress et al. (2003: 172), Uddin (2007: 595), Hughes (2008: 132), Dash (2010: 41), Das et al. (2013: 236); as B. barbata: Clarke (1879: 646), Clarke (1881: 119), Clarke (1890: 25), Burkill (1924: 289), Fischer (1938: 97), Irmscher (1959: 191), Deb (1961: 285), Deb (1981: 268), Chauhan (1996: 174), Chauhan (2000: 424), Kress et al. (2003: 171), Khatun (2008: 9).
Other material
INDIA: Arunachal-Pradesh: Geku, Choudhery 18642 (ARUN n.v.); Puak Camp, Nov. 1911 – Mar. 1912, Burkill 37637 (n.v.); ibid., Nov. 1911 – Mar. 1912, Burkill 36130 (n.v.); Side River, 29 Nov. 1911 – 11 Mar. 1912, Burkill 36080 (n.v.). Assam: Cachar, Jun. 1874, Keenan s.n. (K); ibid., Oct. 1971, Yandell 21 (K); ibid., Dec. 1971, Yandell 65 (K); Cachar, North Cachar Hills, May 1968, Yandell 113 (K); ibid., May 1968, Yandell 114 (K); ibid., Oct. 1971, Yandell 22 (K); ibid., Oct 1971, Yandell 23 (K); ibid., Oct. 1971, Yandell 24 (K); ibid., Nov. 1971, Yandell 48 (K); ibid., Jan. 1972, Yandell 311 (K); Lakhimpur District, Makum, 12 Apr. 1885, Clarke 37809A (BM). Manipur: Eerung River, 27 Nov. 1885, Clarke 42192 (K); ibid., Clarke 42192B (BM); Koupru, Deb 1523 (CAL n.v.); Yhirighat, Nov. 1907, Meebold 5792 (K) [cf. B. thomsonii]. Meghalaya: Khasi Hills, Cherrapunji, 13 Jun. 1850, Hooker & Thomson 16 (syn K 000761431, P); Khasia, Griffith 2576 (K); Jaspa Hill, 20 Jun. 1850, Hooker & Thomson 16 (syn K 000761432); Sillet Hills, 1832, Wallich Cat. No. 3619 (BM). Mizoram: Lushai Hills, Aijal, Sep. 1927, Parry 41 (K); Lushai Hills, Hmuntha, 5 Apr. 1951, Chand 4386 (MICH); Lushai Hills, Sailem, 26 Aug. 1927, Parry 250 (K) [cf. B. thomsonii]; ibid., Jul. 1927, Parry 40a (K); Lushai Hills, Siletalong, Oct. 1926, Parry 36 (K); Lushai Hills, Tingtal, Jan. 1927, Parry 40c (K); Lushai Hills, Zobawk, 5 Jul. 1927, Parry 40b (K) [cf. B. thomsonii]. Tripura: Kumarghat, Deb 2570 (CAL n.v.); Tibruari, Deb 1602 (CAL n.v.); Unokoti Hill, Deb 1139 (CAL n.v.); Vanghmun, Deb 29040 (CAL n.v.).
Description
Rhizomatous, sprawling, monoecious herb, 10–30 cm high. Rhizome: ca 10 mm, villose, internodes 8–12 mm long. Stem: slender, 2–4 mm wide, densely red villose, unbranching. Stipules: lanceolate, 9–20 × 2–6 mm, red villose, persistent. Leaves: petiole 4–14 cm long, densely red villose; lamina ovate to ovate-orbicular, basifixed, base cordate with lobes not overlapping, (3–)6–14 × (2–) 4–10 cm, asymmetric, upper surface dark red to green, densely red strigose all over, underside green to purple, red strigose all over with longer hairs on veins, venation palmate, midrib (2–) 4 –12 cm long; margin entire with teeth at end of veins to denticulate, with long hairs; apex acute. Inflorescence: cymose, terminal and axillary, few; peduncle densely villose, branching twice, primary 1.5–3.5 cm long, secondary 3–5 mm long, with 2– 4 female and 5– 8 male flowers; bracts lanceolate, 7–8 × 2 mm, densely villose, persistent. Male flower: pedicel 8–15 mm long, red villose; tepals 4; outer tepals ovate to oblongelliptic, 8–13 × 5–8 mm, pale pink to pink, red villose on reverse, margin entire, with hairs; inner tepals elliptic, 4–9 × 2–4 mm, pale pink to pink, glabrous; androecium with 35–70 stamens, symmetric; filaments 1–2 mm long, unequal, fused at base; anther oblong elliptic, 1–2 mm long, dehiscing through slits running nearly the entire length of the anther, not hooded, connective extended. Female flower: not seen; ovary 2-locular, placentae bifid; capsule obovoid-ellipsoid, villose, with one long triangular wing and two short crescent wings; styles caduceus. Fruit: recurved; capsule obovoid, 6–14 × 6–9 mm, sparsely villose; wings extending along the pedicel slightly, subequal; longest rounded triangle, 12–30 × 9–18 mm; shortest semi-circular, 2–10 × 8–15 mm.
Distribution and phenology
Northeast India; also in Bangladesh and Myanmar; 250–1800 m. Flowering: October to December; fruiting: November to January.
Conservation status
Least Concern. Begonia thomsonii has an AOO of 80 km 2 and an EOO of 178,250 km 2 with plenty of
suitable habitat available. The species has been found in Bumphabum Forest, Moulling National Park, Khadimnagar National Park and near Muraichhara Eco Park, Blue Mountain National Park and Tawi Wildlife Sanctuary.
Remarks
No specimen was seen with both male and female flowers; however, there is no record of the species being dioecious. Begonia thomsonii is somewhat vegetatively similar to B. scintillans in the herbarium, which is a species with white hairs (not red) on the upper leaf surface and is in general a much smaller species. The inflorescences also differ, bearing only 2–3 flowers per peduncle in B. scintillans (see Fig. 55), unlike the clusters of 5–8 in B. thomsonii. Begonia cathcartii has similar red hairs, although sparser, and is a larger plant, ca 30–60 cm high (not less than 30 cm), with longer inflorescences (ca 10 cm, not less than 4 cm). On some specimens of B. thomsonii the outer tepals have hairs on both sides (Hmuntha, Chand 4386 (MICH), Lushai Hills, Parry 40 (K) and Sillet Hills, J.D.Hooker & Thomson s.n. (K)).
Here we consider B. barbata Wall. ex A.DC (de Candolle 1864) to be a synonym of B. thomsonii, as the only differences are in the density of the indumentum, as noted by Irmscher (1959). Begonia barbata was previously considered a synonym of B. annulata (Kumar 2002); however, the lectotype chosen here is most definitely not that species. Clarke (1879) mentions the possibility of B. barbata, B. griffithii (= B. annulata) and B. thomsonii being conspecific, although here we consider B. annulata to be very distinct. Begonia annulata has a more broadly dentate leaf margin with a silver ring and rough hairs on the upper leaf surface compared to the plain leaves covered in dense soft red hairs in B. thomsonii.
The types for B. barbata (Wallich Cat. No. 3679) consist of several different collections, some of which have been identified as other species; K001112054 is B. hatacoa; K000761430 is a mixed sheet with the specimen in the top left with variegated leaves belonging to B. scintillans, whereas the rest is identified as B. thomsonii. Clarke (1879) noted this in his description of B. barbata and labelled them as 3679A and 3679B, the latter being identified as B. hatacoa (B. rubroveina). Here we decided to lectotypify using Wallich Cat. No. 3679A as this number is clearly marked on the sheet and the material matches the original description; this is on a mixed sheet with B. hatacoa (3679B).
description: Published as part of Camfield, Rebecca & Hughes, Mark, 2018, A revision and one new species of Begonia L. (Begoniaceae, Cucurbitales) in Northeast India, pp. 1-116 in European Journal of Taxonomy 396 on pages 95-97, DOI: 10.5852/ejt.2018.396, http://zenodo.org/record/3787049