A new species of Begonia sect. Diploclinium, Begonia bhutanensis, from Bhutan
Begonia bhutanensis P.Gyeltshen & M.Hughes, sp. nov. (§ Diploclinium) Resembles Begonia rubella in habit, but differs in having fimbriate-laciniate bracts (not entire), rounded wings on the capsule (not elongate triangular), and a symmetric androecium with sub-uniformly sized anthers (not asymmetric with markedly heteromorphic anthers (Rajbhandary et al., 2011).
Plant monoecious, tuberous, herbaceous, 35–50 cm tall. Tuber subglobose, c. 1.9 × 1.6 cm, a creeping tuberous rhizome is also present, c. 4 × 0.8 cm, forming on an adventitious root from near the apex of the tuber. Stem erect or slightly pendent at distal portion, present during flowering, 44–45 cm long, red, glabrous, lowermost internodes 4–6 mm apart, unbranching, 2–4 leaves per stem. Stipules ovate, 1.5–2 × 0.8–1.2 cm, papery, keeled, apex cuspidate, margin entire, adaxial surface glabrous. Leaves alternate; petioles cylindrical, 3–12 cm long, 2–3 mm thick, reddish green, glabrous; lamina broadly ovate, 6–17 × 5- 16 cm, basifixed, base cordate, margin subentire and sparsely white ciliate, apex broadly acuminate, venation palmate-reticulate, veins 5–6; adaxial surface with sparsely scattered appressed white hairs c. 2 mm long; abaxial surface paler green, glabrous. Inflorescences terminal or axillary on stems with 4–5 internodes, bisexual, protandrous, dichasial cymes with 4–5 branches, erect to pendent; peduncles cylindrical, up to 26 cm long, reddish green or green, glabrous, bracts oblong, c. 5 × 2 mm, margin long fimbriate, apex obtuse, base truncate, glabrous. Staminate flower: pedicel c. 1–1.7 cm long, pale green, glabrous; tepals 4, pale pink to pink, margin entire; outer 2 orbicular, 7–9 × 6–8 mm, glabrous, apex and base rounded, margin entire, up to 8-veined; inner 2 narrowly obovate, 6–8 × 3–4 mm, glabrous, apex rounded, base obtuse; androecium loosely globose, stamens c. 20–25, 1–2 mm long, on a c. 2.5 mm column, anthers obovate-oblong, golden yellow, basal anthers sessile, central anthers on a c. 0.5 mm filament, apex rounded and slightly extended. Pistillate flower: pedicel up to 3 cm long, pale green to light pinkish-green, glabrous, tepals 3–4, pale pink to pink, glabrous, margin entire; outer 2 orbicular, 6–8 × 7 10 mm, orbicular, apex rounded, base truncate; inner 1–2 elliptic, 6–7 × 3–5 mm, base sub-obtuse; ovary green sometimes light pinkish on the wings, glabrous, with 3 subequal wings, 3 locules, placentation axillary, 2 branches per locule; styles 3, golden yellow, Y-shaped, c. 3 mm long, fused at base; stigma spiralled, spiral part papillose. Fruits green to pale pinkish green, trigonous-globose, c. 1.7 × 0.6 cm, glabrous; dorsal wing c. 1.7 × 1 cm, slightly falcate at apex, narrower towards the base, lateral wings c. 1.5 × 0.2–0.3 cm.
Phenology. Flowering and fruiting from August to September.
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