One New Species and Four New Records of Begonia (Begoniaceae) from Bhutan
Begonia menchunaensis P.Gyeltshen & M.Hughes is described from the cool broadleaved forest of Punakha District in Bhutan. It is assigned to Begonia sect. Diploclinium because it has a tuberous habit and bifid placentae. Begonia menchunaensis is similar to B. picta Sm. but is distinguished from it by its moniliform tubers (vs single globose tubers); longer petioles up to 10–55 cm (vs 5–12(–20) cm), which are glabrous (vs sparsely puberulous); outer tepals in male and female flowers with an acute apex (vs rounded); and immature ovaries with simple red setose hairs (vs white fimbriate villose hairs). – Type: Bhutan, Punakha District, Toedpisa Block, Menchuna, 2284 m, 24 ix 2021, P. Gyeltshen 067-068 (holotype THIM [THIM17728], isotype THIM [THIM18604]).
Monoecious, tuberous herb, up to 25 cm tall. Tuber stout, moniliform, each section 1–3 cm in diameter, with numerous fibrous roots. Stem 1- or 2-branched, terete, glabrous, up to 20 cm long. Leaves: lamina symmetrical, broadly ovate to triangular-ovate, 15–35 × 10–26 cm, apex acuminate, base cordate, margin shallowly lobed, bidenticulate; adaxial surface green to olive green, white pilose, abaxial surface pale green to brownish green, venation palmate-pinnate, veins c.8, prominent beneath; petiole 10–55 cm long, up to 1.2 cm in diameter, fleshy, pale green to reddish brown, glabrous. Inflorescence terminal, a compressed cyme, appearing umbellate, bisexual, protandrous, 2- to 6-flowered; peduncle pilose when young, unbranched, 5–16 cm long, terete, pale green to lightly brownish red. Staminate flower: pedicels 2.5–4 cm long, erect or curved downwards, pilose, pale green to light brownish green; tepals 4, outer tepals broadly ovate to triangular-ovate, 1.7–2.1 × 1.5–2 cm, apex broadly acute, margin entire or serrate, outer surface sparely red setose, inner surface glabrous, pale pink to white; inner tepals elliptic, 1.2–1.6 × 0.5–1 cm, apex acute, margin entire, outer surface glabrous or a few red setose, whitish pink to white; androecium symmetrical, > 60 stamens, bright yellow; filaments clustered at the base on a column, free, unequal, 0.5–2 mm long; anthers obovate, 1–1.6 mm long, connective rounded, apex obtuse or truncate, dehiscing through lateral slits. Pistillate flower: pedicels 1.5–3 cm long, pilose, pale green or greenish red; ovary green, with 3 unequal wings, with simple red setose hairs, denser on the locular portion; 3-locular, placentation axillary, 2 branches per locule; tepals 5 (or 6), unequal, outer 3 tepals ovate to elliptic-ovate, 1.5–1.8 × 1–1.3 cm, apex acute, margin serrate, outer surface red setose, inner tepals 2 or 3, unequal, elliptic, 1–1.5 × 0.5–0.8 cm, apex acute, margin entire, glabrous, same colour as staminate flower; styles 3, fused at the base, dark yellow, deeply forked once and twisted twice. Capsule oblong-ellipsoid, 1–1.5 × 0.5–0.7 cm, green, with red setose hairs, wings slightly extending along the pedicel, unequal; dorsal wing, narrowly triangular, 3.5–4.6 × 1–1.5 cm, lateral 2 wings short triangular, 8–12 × 2–9 mm, sparsely red setose, warty.
It Flowers in September, fruiting from September to October.
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