Four new species of Begonia sect. Coelocentrum (Begoniaceae) from limestone areas in Guangxi, China

Four new species of Begonia (sect. Coelocentrum), namely B. debaoensis, B. pseudodaxinensis, B. pseudoleprosa and B. semiparietalis, from the limestone areas in Guangxi Zhuangzu Autonomous Region, southern China are described and illustrated. A somatic chromosome number of 2n = 30 is determined for three of them. Begonia debaoensis resembles B. bonii Gagnep., differing in having smaller leaves; a slender rhizome with long internodes; bicolored outer tepals that are pink toward the margins and whitish in the middle; and bearing abnormal, feminized stamens on staminate flowers. It is perhaps of hybrid origin. Begonia pseudodaxinensis is similar to B. daxinensis T.C. Ku, differing in the leaves being entirely green and without white maculation; the stipule apex obtuse or emarginate; and the rhizome stout and nearly glabrous. Begonia pseudoleprosa bears a superficial resemblance to B. leprosa Hance (sect. Leprosae), differing in the fruits being winged, trigonous obovoid-ellipsoid and with parietal placentation. It also resembles B. bonii Gagnep., differing in the leaves being subcoriaceous, nearly flat and very sparsely setulose or subglabrous on the adaxial surface; and petioles and the main veins on the lower leaf surface being appressed hairy. Begonia semiparietalis is also somewhat similar to B. bonii Gagnep., differing in the leaves having white maculation along main veins and the upper surface sparsely setose-pilose; ovaries and fruits long glandular-pilose; placentation parietal on upper half of the ovary and axile on the lower half.