195 Juncus effusus L.

Within this polymorphic, widespread species several lower taxa are distinguished (cf. Hultén, Amphi-atl., p. 172). The species s. str. (var. effusus) is mainly restricted to Europe. The distribution of other taxa in E. and SE. Asia and N. America, is also mapped, although more tentatively. The taxa in eastern N. America have been treated by L. Hämet-Ahti in Ann. Bot. Fenn. 17 /1980, p. 183 ff. The species is reported among the amphi-atlantic plants (Hultén I. cit.). Including var. pacificus Fem. & Wieg. and var. decipiens Buch. it has, however, an almost circumpolar distribution. The species, probably mostly var. effusus, has been introduced into several parts of the world (see the notes in the margin of the map). Cf. also world maps by H. Weimarck Sv. Bot. Tidskr. 40/1946, p. 145, and Meusel et al. 1965, p. 83).