The cytology of four Netherlandic species of Equisetum has been worked out. E. arvense, E. fluviatile and E. palustre are normal and show n = 108, while E. trachyodon is almost a totally asynaptic species with 2n = 216. The results are in complete agreement with those obtained by Manton (1950) for these species. In E. trachyodon the course of meiosis has been critically examined, and it is concluded that this is a hybrid species as has already been suspected by earlier workers. The present-day evolutionary status of the genus has been discussed in the light of cumulative cytological evidence.