A comprehensive study of the critical taxon Leymus ordensis Peschkova was carried out. Inaxactness in the description of morphological characters of the typical specimens was revealed. Natural and experimental populations of L. ordensis from the classical location (ORDL-0430, Irkutsk Oblast, settlement Ust-Orda) and L. chinensis from Irkutsk Oblast and Buryatiya as well as herbarium specimens of L. akmolinensis from different parts of the area were studied. A comparative morpho-logical analysis of diagnostic characters showed the following: i) visible similarity of isotypes of L. ordensis and herbarium specimens of L. akmolinensis ; ii) significant variation of characteristics in experimental plants which had been grown from seeds of natu-ral populations ORDL-0430 and L. chinensis OLHL-0409 (Lake Baikal, Olkhon Is-land); iii) absence of individuals identical to typical L. ordensis specimens in natural and experimental populations ORDL-0430. A higher level of heterogeneity of polypeptide pattern of individual seeds in comparison with that of different populations of L. chinensis was revealed in the population ORDL-0430 by SDS-electrophoresis. The electrophoretic analysis of subfractional composition of histon Н1 showed significant similar-ity of experimental population ORDL-0430 to population OLHL-0409 of L. chinensis from the Olkhon Island (Lake Baikal). It was concluded that independence of L. ordensis , as a species described by just a few herbarium specimens, demands an additional sub-stantiation.Key words: Leymus ordensis, L. chinensis, L. akmolinensis, L. paboanus , taxon, morhpotype, systematics, SDS-electrophoresis, endosperm proteins, histon H1.