11 Equisetum hiemale L.

This polymorphic species occurs in large parts of Eurasia and N. and C. America. In E. Asia and N. America several taxa are distinguished, int. al. var. intermedium A. A. Eat. (syn.: E. laevigatum A. Br.) occupying nearly the entire N. American range on the map, var. californicum Milde (on the map E. laevigatum var. californicum, also named E. hiemale var. affine (Engelm.) A. A. Eat.) in Western N. America, and var. japonicum Milde in Japan (not in Ohwi, Fl. Japan 1965). For the complicated taxonomy and nomenclature, see Hauke in Nova Hedwigia 8/1963. The species s. lat. belongs to the circumpolar plants (Hultén, Circumpol. I, p. 184, 254 and map 174).