SEM studies of some smaller, unornamented desmid taxa of the genera Cosmarium and Euastrum showed that the superficial cell wall pattern of pores and scrobiculations provide useful, auxiliary taxonomic characters. Euastrum lacustre (basionym E. binale var. lacustre Messik.) and E. groenbladii (basionym E. binale forma groenbladii Messik.) are raised in rank and compared morphologically and ecologically with some other, light microscopically very similar species with which they can easily be confused when naming is attempted by means of conventional methods.