Scientific name: Begonia calciphila C.-I PengEnglish name: Vietnamese name: Thu hải đường đá vôiOther name:
Herbs perennial, monoecious, lithophytic. Rhizomes creeping, to 30 cm or longer, internodes 1.5—4.5 cm long, 6-8 mm across, reddish or whitish hirsute, hairs 3-3.5 mm long, glabrescent. Stipules ovate, 7-12 mm long, 4-7 mm wide, apex caudate, margin entire, abaxially hirsute, hairs 1.5-3.5 mm long. Leaves alternate; petiole brownish, 2-7 cm long, villous, hairs 3.5-4 mm long, brownish or reddish; leaf blade orbicular-ovate to ovate, apex acute, base obliquely cordate, 7-10.5 cm long, 5.5-8.5 cm wide, margin undulate, densely ciliate; primary veins 6-8, palmate, veinlets reticulate; adaxially sparsely or densely scabrous, trichomes ca. 1.5 mm long; abaxial surface reddish-hirsute on veins, trichomes multicellular, ca. 1 mm long. Inflorescence axillary, with 2-5 flowers in dichasial cymes, peduncle tinged reddish, ca. 8 cm long, glabrous; pedicel 8-9 mm long, glabrous. Bracts ovate, margin sparingly reddish ciliate, 3.5-4 mm long, 2.5-3 mm wide. Staminate flower: tepals 4, outer 2 orbicular-ovate to ovate, margin entire, white or tinged pinkish, 9-15 mm long, 9-13 mm wide, abaxially sparsely reddish-hirtellous; inner 2 oblanceolate, white, 11-13 mm long, 3.5-4 mm wide; androecium zygomorphic, stamens 20-25, yellow, filaments 0.8-1 mm long, anthers ca. 1.5-1.7 mm long. Carpellate flower: tepals 3, glabrous, outer 2 orbicular or suborbicular, tinged pinkish, 12-14 mm long, 12-13 mm wide, margin entire; inner 1 oblanceolate, 8-10 mm long, 3-5 mm wide, white; ovary trigonous-ellipsoid, pinkish, 7-8 mm long, 4-5 mm across, glabrous, 3-winged, abaxial wing crescent-shaped, 3-5 mm tall, lateral wings 2-3 mm tall; styles 3, ca. 4 mm long, fused to 1/3 at base, bifurcating with yellow stigma forming a continuous U- shaped papillose band. Capsule trigonous-ellipsoid, 7-8 mm long, 4-5 mm across, abaxial wing crescent-shaped to elliptic, 8-9 mm tall, lateral wings crescent shaped, 3-4 mm tall. Seeds many, ellipsoid, truncate at both ends, brownish, 0.4-0.5 mm long, 0.2-0.25 mm thick.
Ecology and distribution
Endemic to limestone karst areas in Cuc Phuong National Park, Ninh Binh Province, Vietnam, elev. 320-400 m. It grows on steep rocky slope surface or rock crevices in semishaded or shady broad-leaved forest