Begonia macrotoma Irmsch.

Herbs, to 40 cm tall. Rhizomes elongate, 5-20 mm in diam. Stems glabrous. Leaves basal and cauline; stipules ovate, ca. 1.9 × 1.2 cm, glabrous; petiole 7-15.5 cm, glabrous; blade oblong, slightly asymmetric, 12-15 × 14-18 cm, abaxially glabrous, adaxially sparsely hirsute, venation palmate, 5-7-veined, base slightly oblique, cordate, margin irregularly serrulate, divided to 2/3 of leaf length; lobes 5-7, apex acuminate; lobules present. Inflorescence glabrous; peduncle 5-15 cm; bracts oval, ca. 13 × 8 mm. Staminate flowers: pedicel ca. 1.9 cm; tepals 4, pink, outer 2 broadly elliptic, ca. 10 × 7 mm, inner 2 ovate, ca. 7 × 5 mm; stamens numerous; filaments 1-2 mm; anthers oblong, 1-1.2 mm; connectives elongate. Pistillate flowers: pedicel 1.4-2 cm; ovary obovoid, ca. 1.2 cm, 2-loculed; placentae axile, bilamellate; tepals ?3, outer 2 broadly elliptic, ca. 1.5 × 1.1 cm, inner 1 elliptic, ca. 12 × 7 mm; styles 2.5-6 mm, fused to halfway; stigmas 2, spiraled. Capsule nodding, obovoid-oblong, 1.5-2 cm × ca. 7 mm, unequally 3-winged; abaxial wing ca. 4 mm; lateral wings smaller. Fl. Aug, fr. Sep.

Yunnan (Lincang, Shuangjiang) [NE India, Nepal, Vietnam].

Forests, by streams; 1200-1500 m.