9 Isoëtes lacustris L.

Besides this European species s. str. the map includes the N. American I. macrospora Dur., which may be regarded as a subspecies or variety of I. lacustris. The closely related I. occidentalis Hend. in W. USA is also tentatively registered on the map. I. lacustris s. lat. belongs to the amphi-atlantic plants (Hultén, Amphi-atl., p. 266 and map 247). Cf. also Meusel et al. 1965, map p. 9. The registration of fossil finds is certainly incomplete.