<i>SPARGANIUM PROBATOVAE (SPARGANIACEAE), </i>A NEW TAXON TO THE EASTERN EUROPEAN FLORA
The localities of <i>Sparganium probatovae</i> Tzvelev ( <i>Sparganiaceae</i>) are cited for the first time for the Eastern European flora. <i>S. probatovae</i> was described from the Arctic part of Kamchatka Territory, and was not known before outside the extreme North-Eastern Asia (Koryak, Okhotsk and Kolyma districts of «Flora of the Russian Far East»). We have found the species among the herbarium materials of Moscow State University Herbarium (MW) from the East Bolshezemelskaya Tundra (Dvina-Pechora floristic district of «Flora of the Eastern Europe»). The species record in the Usa River valley is based on the single herbarium specimen from the Herbarium of the Komarov Botanical Institute RAS (LE). Localities in the Vorkuta vicinities are the most northern ones and the first within the Polar Circle. The taxonomic status of <i>S. probatovae</i> is discussed in the context of its supposed origin from an ancient 102 hybridization ( <i>S. emersum</i> Rehm. X <i>S. hyperboreum</i> Laest.). The diagnostic characters of <i>S. probatovae</i> are supplemented by new material. The previously unknown aquatic form of the species is distinguished; specimens deviating from the type are noted. A solution of the nomenclatural problem which has resulted from the erroneous citation of holotype is proposed.