Begonia acetosella Craib, 1912

Camfield, Rebecca & Hughes, Mark, 2018, A revision and one new species of Begonia L. (Begoniaceae, Cucurbitales) in Northeast India, European Journal of Taxonomy 396, pp. 1-116 : 12-15

Begonia acetosella Craib [sect. Sphenanthera ]

Figs 6–7

Bulletin of Miscellaneous Information, Kew 1912: 153 ( Craib 1912). – Type: Thailand, Chiengmai, Doi Sootep, 21 Mar. 1909, 18°50' N, 98°54' E, A.F.G. Kerr 557 (lecto-: K000761199, designated by Tebbitt 2003a, sheet 2 K000761201; isolecto-: B).

Begonia tetragona Irmsch., Mitteilungen aus dem Institut für allgemeine Botanik in Hamburg 10: 515 ( Irmscher 1939). – Type: China, Yunnan, Mengtze, Henry 10737A (lecto-: B100238046, here designated; isolecto-: E00315022).

Begonia aptera auct . non Blume: Gagnepain in Bulletin du Muséum d’Histoire Naturelle (Paris) 25: 281 (Gagnepain 1919).

Citations in other publications

As B. acetosella: Gagnepain (1919: 282) , Irmscher (1926: 347), Craib (1931: 770), Tebbitt (2003a: 22), Kress et al. (2003: 170), Gu et al. (2007: 161), Hughes (2008: 1), Morris (2010c: 6), Dash (2010: 31); as B. tetragona: Huang & Shui (1999: 12) , Tebbitt (2003a: 22); as ‘ B. aptera ’ auct. non Blume: Gagnepain (1921: 1110), Hô (1991: 729).

Other material

INDIA: Arunachal-Pradesh: Delei Valley, 9 May 1928, Ward 8198 ( K); ibid., 25 Jul. 1928, Ward 8487 ( K); Papum Pare, Toru, Pal. 2009 ( ARUN n.v.); Parsi Parlo, Dash 31716 ( ARUN n.v.); Subansiri District, 8 Apr. 2005, Morris 40 ( CLEMS n.v.).

Description

Caulescent, erect, dioecious herb, 150–200 cm high. Stem: stout, 5–10 mm wide, sparsely puberulous; internodes (5–) 10–20 cm long. Stipules: ovate 8–30 × 3–8 mm, puberulous on reverse, deciduous. Leaves: petiole 1–7(–17) cm long, tomentose; lamina ovate-lanceolate to lanceolate, basifixed, base shallowly cordate, 8–18(–30) × 2–7(–15) cm, strongly asymmetric, upper surface green, sparsely strigose, underside pale green veins tinged red, pubescence on veins, venation palmate-pinnate, midrib 7–15(–24) cm long; margin serrate, toothed at the end of the veins with smaller teeth between, with hairs; apex acuminate. Inflorescence: cymose, axillary, numerous; peduncle puberulous, branching 1–2 times, primary 2–10 mm long, secondary 1–2 mm long, with 1– 3 female flowers or 3– 5 male; bracts ovate, 4–10 × 3–5 mm, deciduous. Male flower: pedicel 4–10 mm long, glabrous or with minute hairs; tepals 4; outer tepals broadly elliptic, 10–18 × 6–15 mm, white to pink, glabrous; inner tepals obovateelliptic, 6–16 × 8 mm, white to pink, glabrous; androecium with 60–100 stamens, symmetric; filaments 1–3 mm long, free; anther oblong-obovate, 1–2 mm long, dehiscing through slits less than half the length of the anther, not hooded, connective extended. Female flower: pedicel 4–10 mm long, glabrous; bracteoles absent; tepals 4, equal, broadly elliptic, outer tepals 8–10 × 5–12 mm, white to pale pink, glabrous, margin entire, inner tepals as in male; ovary 4-locular, placentae bifid; capsule rhomboid, 3–15 × 4–11 mm, glabrous, with 4 equal short triangular wings, glabrous; styles 4, deeply forked once and twisted once, caduceus. Fruit: on stout pedicel, rhomboid, fleshy; capsule 12–15 × 17 mm, glabrous; without wings or with 4 horns.

Distribution and phenology

Arunachal-Pradesh; also in China, Myanmar, Thailand, Laos and Vietnam; 1200–1500 m. Flowering: mainly from February to April; fruiting: mainly from May to July.

Conservation status

Least Concern ( Hughes 2008). Begonia acetosella is a widespread species with no significant change in recent years to warrant a change in its status.

Remarks

Most specimens from the study area were in fruit, so the floral description has been augmented with information from Tebbitt (2003a) and specimens from neighbouring countries. The horn-like structures on the fruits are formed by the short wings when they dry. This species is vegetatively most similar to B. longifolia which differs in being monoecious and also in having 3 styles and 3-locular fruit. When sterile B. acetosella can also be somewhat similar to the two species in Begonia sect. Monopteron ( B. griffithiana and B. nepalensis ), although they usually have shorter, narrower and more linear or oblong leaves and shorter and narrower stipules. The leaves of B. nepalensis can get to a similar width to those of B. acetosella , however, they usually have an entire margin and are hairy only on the underside or glabrous on both surfaces.