The results of cytological investigations on 95 populations from 60 species of mosses are given. These results include studies of gametophyte mitoses from 26 of the species concerned. The technique for obtaining gametophyte mitotic preparations is described. Karyotype comparisons are made within the generaPolytrichumandDicranumand the value of such comparisons is stressed. Where possible gametophytic mitotic observations have been correlated with sporo‐phytic meioses from the same gathering