“…While M. arvensis of Europe has a somatic chromosome number of 72 (Tucker & Fairbrothers, 1990), M. canadensis of North America and Asia has 2n = 96: Canada (Mulligan and Cody, 1968;Gill, 1971;Gill & al., 1973;Chambers & Hummer, 1994), China (Tsuda, 1952), India (Harley & Brighton, 1977;Kundu & Sharma, 1985), Japan (Ruttle, 1930(Ruttle, , 1931(Ruttle, , 1938Tsuda, 1952Tsuda, , 1963Ikeda & Konishi, 1954;Ikeda & Ogo, 1954;Ikeda & Udo, 1955a, b, 1958b, 1966bIkeda & al., 1956Ikeda & al., , 1963Ikeda & al., , 1968Ikeda & al., , 1970Murray, 1960b;Ammal & Sobti, 1962;Sobti, 1965Sobti, , 1971bIkeda & Ono, 1967, 1969a, Russia (Makarov & Reznikova, 1972), and U.S.A. (Gill, 1971;Gill & al., 1973;Chambers & Hummer, 1994). Plants with 2n = 72 from Asia were later shown to be a hybrid of M. canadensis × M. japonica (Ikeda & al., 1970), while those reported for North America with 2n = 72 are probably naturalized plants from Europe (e.g., Löve & Löve, 1982a).…”