The hybrid between the aquatic plants Sagittaria natans, of boreal Eurasia, and S. sagittifolia, of temperate Europe and W Asia, is widespread in the area of N Europe (Sweden, Finland, Russia) where the ranges of the two species overlap. The hybrid, which is variously intermediate between its parents, is described as S. x lunata C.D. Preston & Uotila. Its known distribution is mapped and its habitat, reproduction and dispersal are summarised. In Norden (= Fennoscandia and Denmark) it occurs in many watercourses in the absence of one or both parents, suggesting that it has a relict distribution, and it extends further north than S. sagittifolia and further north and south than S. natans. In the Finnish provinces at the northern end of the Gulf of Bothnia there is a hybrid complex which includes plants which approach S. sagittifolia, but only a single specimen of typical S. sagittifolia is known from these regions. S. sagittifolia forma xanthandra Holmberg, described from Sweden, appears to have been a non-persistent variant of S. sagittifolia with yellow anthers rather than a hybrid with S. natans. — Flora Nordica Notes 34
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