Abstract
Brazil is a megadiverse country that intends to catalog all its flora by 2020. Therefore, knowledge about taxonomy and the correct identification of species is essential for accessing the real species biodiversity. Macromitrium (Orthotrichaceae) is considered the third largest moss genus in the world and with the majority of its species distributed in tropical and subtropical regions. For Brazil 64 species have been cited, but 44 remain as unknown to the Brazilian flora. The aim of this work was to check all 64 names of Brazilian Macromitrium helping to clarify its validity and correct identification. Type specimens from 14 herbaria were studied using optical microscopy. After this analysis 22% are good species, 54% are synonymous of others species; 13% are excluded from the Brazilian flora and 11% were not possible to check. This work contributed to clarify the diversity of Macromitrium in Brazil, contributing to the knowledge of bryophytes and important data for the flora of Brazil 2020.