-(Taxonomic aspects of Schizomeris Kützing (Chaetophorales, Chlorophyta)). Schizomeris Kützing is a filamentous alga without ramifications and with differentiated basal attachment system. The genus contains the type species Schizomeris leibleinii Kützing and the two poorly known species S. irregularis Fritsch & Rich and S. indicum (Ghose) Fritsch & Rich. The species are differentiated mostly by the basal attachment system type. However, the specific taxonomy of the genus is confused. Morphometrical and morphological studies were conducted in populations identified as S. leibleinii according to two approaches. In the first one, 11 populations from different localities were analyzed and in the second, two distinct populations were monthly evaluated during 11 months. Diameter of multiseriate filaments, diameter and length of cells from multi and uniseriate filaments, presence of constriction, form of filament summit, and basal system type were evaluated in both approaches. In addition, karyological studies were conducted to complement taxonomic information. Results revealed a wide morphological variation, being more accentuated among populations from different localities than in the same populations along the time, but the characteristics showed a continuous gradient. The different types of the basal system described for the species of the genus (bluntly rounded, holdfast disc, lobed and rhizoid) were found in the populations studied. These findings suggest that distinction among the three species is very fragile and cannot be supported by differentiation of the basal system or metrical characteristics. Based on present results we consider that Schizomeris is composed by a single species. Karyological analyses resulted in n = 12, differing from previous studies and some possible explanations are discussed.Key words -Chaetophorales, karyology, morphological variation, Schizomeris leibleinii, taxonomy RESUMO -(Aspectos taxonômicos de Schizomeris Kützing (Chaetophorales, Chlorophyta)). Schizomeris Kützing é uma alga filamentosa sem ramificações e com sistema basal de fixação diferenciado. O gênero contém a espécie-tipo Schizomeris leibleinii Kützing e duas espécies pouco conhecidas, S. irregularis Fritsch & Rich e S. indicum (Ghose) Fritsch & Rich. As espécies são diferenciadas, principalmente, através do tipo de sistema basal de fixação. Contudo, a taxonomia específica do gênero é confusa. Estudos morfométricos e morfológicos foram realizados em populações identificadas como S. leibleinii de acordo com duas abordagens. Na primeira, foram analisadas 11 populações de diferentes localidades e na segunda, duas populações distintas através de coletas mensais durante 11 meses. O diâmetro de filamentos multisseriados, diâmetro e comprimento de células de filamentos multi e unisseriados, presença de constrição, ápice dos filamentos e tipo de sistema basal foram analisados em ambas abordagens. Além disso, estudos cariológicos foram efetuados para complementar as informações taxonômicas. Os resultados revelaram ampla ...