Cytotaxonomy of section Psammelymus of the genus Elymus

Comparative studies were made on the morphology of herbarium specimens and plot-grown plants of three species of Elymus L. in section Psammelymus Griseb. in Ledeb., namely, E. racemosus Lam., E. arenarius L., and E. mollis Trin. The three species were morphologically and geographically distinct. Elymus racemosus, a tetraploid species (2n = 28), occurs from Eastern Greece to Altai. Elymus arenarius is a Northern European species that is octoploid (2n = 56); it occurs in Iceland and has been introduced to the west coast of Greenland and widely separated localities in North America. Elymus mollis (2n = 28) has a wide distribution from the North Pacific coasts to Southern Greenland and rarely Iceland; it occurs in the Arctic from the Taimyr Peninsula to West Greenland. In E. mollis, there are three subspecies: (1) subsp. mollis including var. mollis f. mollis, f. simulans f. nov. and f. scabrinervis f. nov. and var. japonicus var. nov.; (2) subsp. villosissimus (Scribn.) Love; and (3) subsp. interior (Hultén) comb. nov. The Asiatic species, E. angustus Trin. and E. dasystachys Trin., are related to these three species. Elymus × vancouverensis Vasey appears to be an interspecific hybrid complex that originated from the hybridization of E. mollis var. mollis and probably E. triticoides Buckl., which is also tetraploid (2n = 28). In E. × vancouverensis, there are three nothomorphs: nm. vancouverensis (2n = 42), nm. californicus nm. nov. (2n = 42), and nm. crescentianus nm. nov. (2n = 28).