Silva, Anádria Stéphanie da creator Ribeiro, André Rodolfo de Oliveira creator Sousa, Mayco Werllen dos Santos creator Fagg, Christopher William creator Falcão, Rosana creator Oliveira, Regina Célia de creator text periodical abstract or summary bl. continuing eng Abstract Mesosetum is a Neotropical genus with 25 species, and 21 of them occur in Brazil. Mesosetum forms a clade closely related with Keratochlaenarigidifolia and Tatianyx arnacites. The objective of this work was to establish the taxonomic value of the upper anthecium micromorphology for the group. A total of 96 specimens, representing all Mesosetum species(except M. wrightii), K. rigidifolia and T. arnacites were examined under a scanning electron microscope (SEM). PCA and UPGMA analysis were applied using the micromorphological characters. Fifithteen useful taxonomic characters were identified. We highlight the following characters to distinguish the Mesosetum species: the presence, type and distribution of papillae on the abaxial surface of the upper lemma; the presence of unicellular macrohairs and bicellular microhairs; presence or absence of silica cells and the structure of the germination lid. The present work shows that the micromorphological characters identified are important taxonomically at the specific level, allowing the species identification in many cases. Key words: Grass, Keratochlaena, Tatianyx, PCA, UPGMA. Publicação on-line; 33 ref.; 3 tables; 4 illus.; Summary (En) MORFOLOGIA VEGETAL GRAMÍNEA TAXONOMIA POACEA Rio de Janeiro-RJ Jardim Botanico do Rio de Janeiro 1935 2025-1431 0370-6583; 2175-7860 on-line BR2025000188 v. 66(2) p. 645-657; (2015) https://www.scielo.br/j/rod/a/ZR3FsLYV4vnnK4NpDZNnQGm/?format=pdf&lang=en https://www.scielo.br/j/rod/a/ZR3FsLYV4vnnK4NpDZNnQGm/?format=pdf&lang=en BR-BrBNA 250313 20250313101133.0 eng