625 Alnus incana (L.) Moench

This polymorphic species s. lat. is widely distributed in Eurasia and N. America. It includes the European A. incana s. str. (subsp. incana) with its var. virescens Wahlenb. in the northern parts of the area, further subsp. hirsuta (Turcz.) Hult. in C. and E. Asia and subsp. tenuifolia (Nutt.) Breit. in western N. America merging into subsp. rugosa (Du Roi) R. T. Claus. in eastern N. America. The species s. lat. belongs to the circumpolar plants (Hultén, Circumpol. Il, p. 134, 356 f. and map 126). Cf. also Meusel et al. 1965, map p. 120. For A. crispa (Ait.) Pursh in N. America, see Porsild and Cody 1980, map 443.