Begonia (sect. Platycentrum) xanthina Hook. (Hooker 1852
Creators: name: Camfield, Rebecca
name: Hughes, Mark
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Cucurbitales
Begoniaceae
Begonia
Begonia xanthina

description: Begonia xanthina Hook. [sect. Platycentrum]
Figs 65–66
Botanical Magazine 78: tab. 4683 (Hooker 1852).
– Type: Cultivated collection, 1852, Nuttall s.n. (lecto-: K000739937, here designated). Cultivated at Rainhill, near Preston, from vegetative material collected in the wild from Bhutan in 1850 by Booth.
Begonia xanthina var. lazuli Hook., Botanical Magazine 85: tab. 5107 (Hooker 1859). – Begonia lazuli Linden, La Belgique Horticole 8: 166 (Linden 1858), nom. nud. – Begonia lazuli Linden & C.Koch ex K.Koch, Wochenschrift für Gärtnerei und Pflanzenkunde 1: 339 (Koch 1858). – Type: Hooker (1859) tab. 5107 [illustration].
Begonia xanthina var. pictifolia Hook., Botanical Magazine 85: tab. 5102 (Hooker 1859). – Type: Hooker (1859) tab. 5102 [illustration].
Begonia poecila C.Koch ex K.Koch, Wochenschrift für Gärtnerei und Pflanzenkunde 1: 338 (Koch 1858). – Type: unknown.
Citations in other publications
As B. xanthina: Koch (1858: 340), Clarke (1879: 644), Clarke (1881: 119), Grierson (1991: 245), Gu et al. (2007: 204), Uddin (2007: 595), Dash (2010: 41).
Other material
INDIA: Arunachal-Pradesh: Bhalukpung, Jul. 1970, Yandell 116 (K); Geku, Choudhery 16395 (ARUN n.v.); Lohit Valley, 17 Feb. 1950, Ward 19163 (BM) [aff. B. xanthina]; Mirir Hills, Jan. 1973, Yandell 225 (K); Mishmi Hills, 1862–1863, Griffith 2591 (K). Meghalaya: Khasi Hills, Nov. 1886, Mann s.n. (K).
Description
Rhizomatous, monoecious herb, 30–60 cm high. Rhizome: 15–20 mm wide, pilose. Stipules: lanceolate, 15–20 × 8–10 mm, puberulous on midrib, caduceus. Leaves: petiole 12–25 cm long, pilose to villose; lamina ovate to broadly ovate, broadly bullate, basifixed, base cordate with lobes not overlapping, 14–21 × 10–14 cm, slightly asymmetric to asymmetric, upper surface dark green with white/pale green spots between veins, or dark green without spots, sometimes with blue iridescence, glabrous or very sparsely pilose, underside dark red/purple, with or without metallic blue shine, pilose all over, denser on main veins, venation palmate, midrib 10 –15 cm long; margin entire to undulate, with sparse hairs; apex acute. Inflorescence: cymose, terminal, few; peduncle glabrous, branching 2–3 times, primary 13–19 cm, secondary 1–5 cm, tertiary 3–6 mm, with 2– 4 female and 4– 6 male flowers; bracts ovate, 20–22 × 18–20 mm, glabrous. Male flower: pedicel 35 mm long, glabrous; tepals 4; outer tepals 10–12 × 5 mm, yellow, puberulous on reverse, entire; inner tepals ovate, 7–12 × 4–6 mm, yellow, glabrous; androecium with 80–160 stamens, symmetric; filaments 1 mm long, fused at base into a short column; anther oblong, 1 mm long, dehiscing through slits about half the length of the anther, connective extended, acuminate on apical stamens. Female flower: pedicel 15–30 mm long, glabrous, bracteoles absent; tepals 5, equal, obovate, outer tepals 16–20 × 7–11 mm, yellow, puberulous on reverse to glabrous, inner tepals similar yet smaller; ovary 2-locular, placentae bifid, ellipsoid, with one long triangular wing and two short crescent wings, glabrous, styles 2, forked once and twisted twice, deciduous. Fruit: recurved; capsule ovate-triangular, 15 × 7–9 mm, glabrous; wings extending along the pedicel slightly, subequal; longest rounded triangle, 20–23 × 10–14 mm; shortest semi-circular, 4–6 × 11–14 mm.
Distribution and phenology
Arunachal-Pradesh and Meghalaya; also in China, Nepal, Sikkim, West Bengal and Bhutan; 600– 1800 m. Flowering: June to September; fruiting: June to October.
Conservation status
Least Concern. Begonia xanthina is found throughout the Eastern Himalayas and into China where there is plenty of suitable habitat. This species has been found in Pakke Tiger Reserve of Bhutan and near the Moulling National Park of Arunachal-Pradesh.
Remarks
The stamens have distinctive very long connectives and are arranged in a cylindrical androecium. The description for the female flowers was augmented using Peng & Leong (2006). The only other yellow flowered Begonia in the study areas is B. flaviflora which has deeply lobed leaves. The leaves can appear similar to B. iridescens (which has pink flowers) as they share white markings on the upper surface and a blue iridescence, but B. iridescens has a more rounded leaf lamina with denser hairs on the veins and shorter petioles.
There are two varieties listed by Hooker (1859) which are no longer recognised; var. pictifolia having white spots/stripes on the surface of leaves and var. lazuli with a blue iridescence. Specimens can also gain a metallic blue shimmer on the underside of their leaves upon drying as seen in Yandall 225, even though that was noted as being dark red when collected. Begonia lazuli was described from living plants
grown by Linden so no type specimen exists, thus the drawing of B. xanthina var. lazuli in the Botanical Magazine becomes the type.
The two Koch names B. poecila and B. lazuli have no type specimens mentioned in the protologues and the descriptions were most likely based on cultivated living material. Begonia × marmorea Van Houtte ex Planch. (Planch 1854) is B. xanthina × B. rubroveinia (B. hatacoa), erroneously considered a synonym (Govaerts 1996). The type for this hybrid is the colour plate included in Planch (1854), which lacks the yellow flowers of B. xanthina.
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 102-105, DOI: 10.5852/ejt.2018.396, http://zenodo.org/record/3787049