2. Begonia gracilifolia Y.M.Shui, Nuraliev & Aver., sp. nov. (Fig. 2)

B. sect. Petermannia (Klotzsch 1854: 124) de Candolle (1859: 128).

Diagnosis:— Similar to B. rubrosetosa Aver. in Averyanov & Nguyen (2012: 20) and B. saolaensis Y.M.Shui, T.A.Le & C.T.Vu in Shui et al. (2019a: 61), differing in glabrous stem, petiole, leaf blade, pedicel and ovary, stipules 4–8 × 1.5–3 mm, narrowly oblong-lanceolate leaf blade, tepals of staminate flowers 2–3.5 mm long, tepals of pistillate flowers 3–4.5 mm long and abaxially hairy, styles 1 mm long.

TYPE:— VIETNAM. Quang Nam Province: Nam Giang District, Song Thanh Nature Reserve, in the forest, river bank, 15°33’55’’N 107°23’15’’E, elev. 1000 m, 27 April 2019, Nuraliev M. S. 2425 (holotype MW: MW0595740; isotypes E, MW: MW0595741; photos LE: LE01093019 http://en.herbariumle.ru/?t=occ&id=43974) .