NEW SPECIES OF THE GENUS PHYSARUM (MYXOMYCETES = MYXOGASTREA) FOR RUSSIA

Three new species for Russia: Physarum subnutans, P. gravidum, and P. caesiellum are reported for Russia. For each species, photographs of sporocarps and light and electron microscopic images are provided. The morphology of the specimens belonging to P. caesiellum are also fi ts the description of P. pseudocolumellatum (syn. P. columellatum var. «macrosporum»), but these taxa have never been validly published. For this reason we propose to use the name P. caesiellum for both last taxa. However, to confi rm the synonymy of these names, a comparative study of type specimens of P. caesiellum and P. pseudocolumellatum MM 18066 is necessary. The data obtained signifi cantly expand our understanding of the ranges of the species under discussion.