黄瓣秋海棠 huang ban qiu hai tang

Herbs, to 40 cm tall. Rhizomes elongate. Leaves basal; stipules caducous, ovate to narrowly triangular, margin entire, apex acuminate to cuspidate; petiole 15-23 cm, subglabrous to sparsely pilose; blade broadly ovate, asymmetric, 17-26 × 15-22 cm, abaxially subglabrous or remotely pilose, adaxially glabrous, venation palmate, base oblique, cordate, margin remotely and finely serrulate, apex acute. Inflorescences glabrous; bracts ovate, to 2.3 × 1.8 cm, glabrous, margin entire, apex acute. Staminate flowers: pedicel 1.5-2 cm; tepals 4, yellow, glabrous, outer 2 elliptic, 2.1-2.2 × 1.2-1.3 cm, inner 2 narrowly obovate, ca. 2 × 0.9-1 cm; stamens numerous; filaments fused to halfway; anthers oblong, apex acute. Pistillate flowers: tepals 5, yellow, glabrous, unequal, obovate to oblong, largest 1.5-2.2 × 1.4-1.6 cm, smallest 1.2-1.6 × 0.8-1.3 cm; ovary glabrous, 2-loculed; placentae axile, bilamellate; styles 2; stigmas 2-cleft, spiraled. Capsule nodding, unequally 3-winged; abaxial wing falcate, ca. 1.7 cm; lateral wings smaller. Fl. Sep-Oct, fr. Nov.

Forests, rocky hills by streams; ca. 800 m. SW Yunnan [NE India].

Begonia xanthina is a new distributional record reported for China by Peng et al. (Bot. Stud. 47: 92. 2006). It resembles B. rex but differs by the yellow tepals and the leaves, which lack long, setose hairs and the horseshoe-shaped spot.