635 Urtica dioica L.

This polymorphic species is indigenous in Eurasia. As it has long followed the settlements of the white man, it is often difficult or impossible to distinguish naturalized occurrences from the native population. Thus, the map is composed of native as well as naturalized occurrences. A group of closely related species in N. America, most probably hybridizing with each other and with the introduced U. dioica, is mapped separately. There are more known occurrences in N. America than those which are marked by dots. Further, U. dioica is introduced into Africa and C. and S. America and into other parts of the southern hemisphere. The ranges of the N. Scandinavian var. sondenii Simmons and the S. Russian var. pubescens Trautv. as well as the E. Asiatic U. angustifolia Fisch. are shown on a separate map (no. 636). U. dioica s. lat. belongs to the circumpolar plants (Hultén, Circumpol. Il, p. 294 and map 285). Cf. also Meusel et al. 1965, map p. 124.