662 Rumex aquaticus L. s. lat.

This polymorphic and widespread species is here represented by four subspecies, viz. subsp. aquaticus in Europe and W. Asia, merging into subsp. protractus Rech., which occurs in large areas of Asia and possibly also in N. Russia, further subsp. fenestratus (Greene) Hult. in easternmost Asia and through N. America and subsp. occidentalis (Wats.) Hult. in western N. America. The distribution limits are for the mast part tentatively drawn. The species s. lat. belongs to the circumpolar plants (Hultén, Circumpol. Il, p. 132 and map 123). Cf. also Meusel et al. 1965, map p. 128. A closely related species, R. aquaticiformis Rech. f., occurs in Patagonia.