19 Equisetum arvense L.

This variable species is widely distributed in Eurasia and N. America. Among the numerous varieties the var. boreale Milde occurs in the northern part of the area. Occasionally this species is found in places outside the map area, e.g. in Mexico, S. America, S. Africa and New Zealand, introduced there by man. It is still insufficiently known in remote areas in N. Siberia and Canada. It belongs to the circumpolar plants (Hultén, Circumpol. I, p. 106 and map 98).