POTAMOGETON X BENNETTII FRYER (=POTAMOGET ON-CRISPUS X TRICHOIDES), ANEW HYBRID FOR THE EUROPEAN CONTINENT IN ALSACE, 2ND OCCURRENCE IN THE WORLD

In 1984, an new Potamogeton has been found in Alsace (France) and prov ed to be the hybrid P. crispus x trichoides. Its most important featur e is the reduced number of carpels (2-3). The cultivation of the taxon has facilitated its determination. This hybrid was hitherto known onl y from Scotland. The two populations in the upper Rhine plain of Alsac e are living in moderately polluted running water influenced by ground -water. Consequently the accompanying species in the phytosociological table arc rarely mesotrophic but mostly eutrophic. In 1994, the size of the populations of the hybrid seemed still to be nearly constant.