106 Potamogeton friesii Rupr.

This widespread species occurs in large parts of Europe (except extreme N and S) and in adjacent parts of Asia. Further, there are scattered localities in C. and E. Asia. Finally, there is a wide distribution area in N. America. However, the distribution is on the whole incompletely known, and several reports are not confirmed. Cf. also Meusel et al. 1965, map p. 25.