AbstractSpores of ten North European species of the genusTortulaHedw. were studied in the transmission electron microscope. In all the sporoderm was more or less covered with finely papillate processes of several different types which divide the genus into a number of groups different from the previously suggested sections. The ornamentation of leaves, peristomes, and spores ofT. norvegica(Web. f.) Wahlenb. has been studied in the scanning electron microscope. The leaf papillae are not c-shaped as suggested in the literature, but branched in a rather complex way. The borders of the basal membrane cells of the peristome appeared to be a continuation of the filamentous portion of the teeth. A comparison withT. ruralis(Hedw.) Gaertn., Meyer&Scherb. revealed the ornamentation to be of the same basic type in the two species.