Abstract
From the Netherlands, five desmid species are described as new to science: Cosmarium arcuatiporosum, Cosmarium logiensiforme, Cosmarium mandosii, Euastrum neogutwinskii and Euastrum dubioides. Furthermore, Euastrum binale var. tumoriferum is raised to species level with the name Euastrum tumoriferum. The affinity with similarly looking taxa is discussed.