Begonia handelii Irmsch. [sect. Sphenanthera] Fig. 27 Anzeiger der Akademie der Wissenschaften in Wien. Mathematische-naturwissenchaftliche Klasse 58: 24 (Irmscher 1921). – Type: Vietnam, Tonkin, 1 Nov. 1914, Handel-Mazzetti 12 (lecto-: WU0038802, here designated; isolecto-: B100169832, E00051632 n.v., WU1924-0004735). Begonia tessaricarpa auct. non. C.B.Clarke: Dash in Bulletin of Arunachal Forest Research 26: 41 (Dash 2010). Citations in other publications As B. handelii: Irmscher (1927: 348), Handel-Mazzetti (1931: 385), Irmscher (1939: 517), Chun & Chun (1939: 22), Yu (1948: 115), Hô (1991: 733), Tebbitt (2003b: 1), Tebbitt (2005: 208), Hughes (2008: 47). Other material INDIA: Arunachal-Pradesh: Palin to Yanglang village, Dash 31147 (ARUN n.v.). Assam: Digboi, 9 Mar. 1947, Ward 16090 (BM 000017315). Description Rhizomatous, dioecious herb, 20–40 cm high. Rhizome: ca 10 mm wide, glabrous, internodes 10–15 mm long. Stipules: ovate, 9–14 × 4–5 mm, glabrous, persistent. Leaves: petiole (5–) 10–25 cm long, puberulent to glabrous; lamina ovate to lanceolate-ovate, basifixed, base cordate with lobes not overlapping, 12–20 × 6–11 cm, asymmetric, upper surface green, glabrous or sparsely puberulent, underside pale green, glabrous or sparsely puberulous, denser on veins, venation palmate, midrib 8–16 cm long; margin entire to sparsely dentate, glabrous, apex acute to acuminate. Inflorescence: cymose, axillary, many, secondary branches reduced and appearing sub-umbellate; peduncle glabrous, male primary 3–8 cm, 3–5 flowers, female primary 3–6 cm, 2–4 flowers; bracts ovate, 10–20 × 5–10 mm. Male flower: pedicel 4–10 mm long, with minute hairs; tepals 4; outer tepals orbicular to broad ovate, (15–)20– 55 × (10–) 20–50 mm, white to pale pink, minute hairs on reverse, margin entire; inner tepals oblongelliptic, (10–)15–30 × 5–17 mm, white, glabrous; androecium with 70–100 stamens, symmetric; filaments 2–3 mm long, subequal, free; anther linear-oblong, 2–3 mm long, dehiscing through slits running nearly the entire length of the anther, not hooded, connective extended. Female flower: pedicel 20–30 mm long, with minute hairs; bracteoles absent; tepals 4, unequal, ovate to elliptic, outer tepals 20–50 × 8–10 mm, pale pink, minute hairs on reverse, margin entire, inner tepals as in male flowers; ovary 4-locular, placentae bifid; capsule obovoid to obpyramidal, 6–12 × 6–10 mm, sparsely red pubescent, with 4 small fleshy wings/ridges; styles 4, forked and twisted twice, deciduous. Fruit: on a stout pedicel; pyramidal-turbinate, fleshy; ca 12 × 10 mm, sparsely red pubescent to glabrous, with 4 ridges. Distribution and phenology Arunachal-Pradesh and Assam; also in Southern China, Myanmar, Thailand and Vietnam; 200– 900 m. Flowering: January to March; fruiting: February to April. Conservation status Least Concern (Hughes 2008). Begonia handelii is a widespread species with no significant change in distribution in recent years to warrant a change in its status. Remarks Begonia handelii is remarkable for the size of its flowers, which measure 10 cm across on the holotype of the type variety. This species is variable across its broad geographic range, especially with respect to the indumentum on the petioles and leaves. It is allied to the other dioecious species in sect. Sphenanthera with 4-locular fruit, in the study area represented by B. burkillii and B. tessaricarpa. Begonia burkillii differs in having variegated leaves, male inflorescences with some second-order branching (subumbellate in B. handelii) outer tepals acute (rounded in B. handelii) the stamens in a globose cluster (lax and rosette-like in B. handelii); the shape of the fruit also differs with B. burkillii having a more elongate capsule than the shorter obpyramidal fruit of B. handelii. The fruit of B. handellii is very similar to that of the poorly understood B. tessaricarpa but the flowers and leaves on the type of the latter are smaller and have much longer petioles; the latter is potentially synonymous with B. handellii var. prostrata (Irmsch.) Tebbitt (Tebbitt 2003b, basionym: Irmscher 1939) but we refrain from reducing the name here until better material becomes available. Begonia handellii var. prostrata is likely to occur in the study region but lacks any herbaria records. This variety differs from B. handelii var. handelii by having flowers half the size. Although Tebbitt (2003: 1) cites the WU specimen as the holotype, the B specimen is annotated as such. As the protologue does not cite any herbaria, we have lectotypified the name here to clarify the status of the material in B and WU.

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 41-43, DOI: 10.5852/ejt.2018.396, http://zenodo.org/record/3787049