A New Endangered Species of Senna (Leguminosae) from the Atlantic Forest of Bahia, Brazil, Supported by X-ray Analysis of Leaflets

— Senna (Leguminosae, Cassiinae) is a speciose genus widely distributed throughout tropical and subtropical regions of the world. During taxonomic studies of Senna sect. Chamaefistula ser. Bacillares, a new endemic and endangered species from the Atlantic Forest of Bahia, Brazil was discovered. The new species, Senna bahiensis, is compared with its morphologically similar species Senna gardneri, including x-ray analysis comparison of their leaflet venation patterns. The use of high resolution x-ray digital images provided the decisive information, being a promising technique to be used in systematic studies.