This paper presents a taxonomic study of the species of the genus Senna occurring in Rio Grande do Sul State, Southern Brazil. Nineteen species were found and the occurences of Senna aphylla (Cav.) H.S. Irwin & Barneby, S. araucarietorum H.S. Irwin & Barneby, S. pendula (Willd.) H.S. Irwin & Barneby, S. scabriuscula (Vogel) H.S. Irwin & Barneby and S. spectabilis (DC.) H.S. Irwin & Barneby are recorded for the first time in Rio Grande do Sul. Analitical key, species descriptions and illustrations are presented. Additional informations are provided concerning geographic distribution, habitats, common names and economic uses.
Leguminosae; Caesalpinioideae; Senna; taxonomy; Rio Grande do Sul; Brazil
