B. tamdaoensis

Herbs monoecious, perennial, rhizomatous. Rhizomes 4–7 mm across, to 10 cm long; erect stems seen only at anthesis, to 27 cm tall, ca. 4 mm thick, hispid. Stipules narrowly ovate to triangular, ca. 5 mm long, 4 mm wide, margin entire, keeled, apex aristate, arista ca.1 mm long, sparsely hispid. Leaves alternate, petiole to 15 cm long, hispid; leaf blade ovate or elliptic, asymmetric, 8–12 cm long, 5–8 cm wide, glabrous or subglabrous above, tomentose along nerves beneath, base slightly obliquely-cordate, margin very shallowly divided, irregularly serrulate and ciliate; apex acute to acuminate; venation palmate-pinnate. Inflorescences axillary, protandrous, to 25 cm long, with 4–12 flowers; peduncles 5–21 cm long, hispid; bracts persistent, lanceolate to triangular, apex acuminate, to 5 mm long, margin sparsely fimbriate. Staminate flower: pedicel 1.2–2.3 (–2.8) cm long, glandular-hispid; tepals 4, pink, apex obtuse, outer 2 ovate or narrowly so, 0.8–2 cm long, 0.4–1.2 cm wide, hispid abaxially, inner 2 narrowly oblong or oblanceolate, 0.8–1.8 cm long, 2–6 mm wide; androecium zygomorphic, stamens 12–35, yellow, clavate; filaments 0.5–2.3 mm long, fused at base, anthers 1.6–1.8 mm long. Carpellate flower: pedicel 1.5–2.1 cm long, glandularpilose; ovary unequally 3-winged, glandular-hispid, 2-locular; placentae axile, bilamellate; tepals 5, pink, unequal, oblanceolate, oblong or ovate, 1.5–1.8 cm long, 0.4–1.3 cm wide, hispid outside, apex obtuse; styles 3, fused at base, 2-cleft, stigmas in a spiralled band around style apex. Capsule nodding, unequally 3-winged, abaxial wing ligulate or falcate, 11–19 mm tall, lateral wing ca. 3 mm tall. Begonia tamdaoensis is assignable to sect. Platycentrum by being rhizomatous, protandrous, staminate flowers basal and pistillate flowers distal, ovaries 2-locular and placentas with two branches, capsules pendulous, 2-loculate and wings very unequal (Doorenbos et al. 1998). The capsules are recurved, which is likely an adaptation for rain splash dispersal (Tebbit et al. 2006). However, it is unusual in having 3-styled carpellate flowers. Begonia versicolor Irmscher (1939: 546) is the only other species in sect. Platycentrum that is known to have 3-styled carpellate flowers and 2-loculed ovaries (Shui et al. 2002; Gu et al. 2007). Begonia tamdaoensis resembles B. oreodoxa Chun & F. Chun ex C.Y. Wu & T.C. Ku (1995: 274) in SE Yunnan (China) and northern Vietnam in aspect and being very pubescent, but is distinguished by the very shallowly cordate leaves (vs. cordate), bracts fimbriate (vs. incised), carpellate flower with 5 tepals (vs. 4 or rarely 3) and 3 styles (vs. 2), placentas axile throughout (vs. axile for the most part, but parietal near summit of ovary).

• Classification: Species
• Plant Type: Unknown
• Botanical Section: Platycentrum
• Origin: Asia, N Vietnam
• Originator: C.-I Peng
• Date of Origin: 2015