A NEW SPECIES OF BEGONIA (BEGONIACEAE, SECT. PLATYCENTRUM) FROM THE SIANG VALLEY OF ARUNACHAL PRADESH, INDIA

Begonia siangensis sp. nov., a rhizomatous, procumbent herb, from the Upper Siang District of Arunachal Pradesh, India, is described and illustrated. The species, belonging to the section Platycentrum, is morphologically similar to Begonia iridescens but can be readily differentiated by the subequal and decurrent wings of its ovary, drooping pistillate flowers, and papillose abaxial surface of the leaf. Line drawings, photographs, and a table of characters that distinguish this species morphologically from similar species is provided, as is a key to the Indian species of Begonia sect. Platycentrum.