Observations during six successive years in a cultivated clone of Equisetum arvense L. var. serotinum F. W. Meyer made it possible to study various types of fertile, sterile, and homophyadic stems developing in this clone. As E. arvense var. varium Milde, E. arvense f. sanguineum Luerss., and E. arvense f. compactum Klinge turned out to grow from one single rhizome, it could be concluded that they are mere modifications, generated by soil conditions, aeration and irrigation.