Some Interspecific Crosses in Calamagrostis and Their Evolutionary Consequences

N 1941 a hybrid was obtained in a cross between the two amphimictic I species Calnmagrostis nrundinncea (L.) ROTH (2n = 28) and C .epigeios (L.) ROTH (2n = 56).The former species was used as mother.The chromosome number of the hybrid was determined as 2n=42.The F , plant did not flower until 1944, but since that year it has developed about 200 panicles or more every summer.The hybrid looks rather like C. epigeios, but its laminae have the same pale green shade as is typical of C. arundinacea.When in 1945 the meiosis of the hybrid was examined, great similarities to the apomictic Calctmagrostis species were found ( NYGREN, 1946, p. 239).On the male side there were serious disturbances, most P.M.C.'s forming plasmodia by fusion of solitary P,M.C.'s or whole loculi.In such cases, as a rule, no divisions at all started, the plasmodia degenerating sooner or later.The few P.M.C.'s going trough meiosis dfeveloped pollen containing most chromosome numbers between 2 1 (or lower numbers) and 84.On the female side the meiosis was as disturbed as on the male side, but here, besides the reductional division, the mitotic one occurred, which is characteristic of many apomic tic genera (cf.GUSTAFSSON, 1946).Some panicles of the hybrid were bagged, but no seedlings were obtained.On the other hand, 49 F , plants were obtained, with some difficulties, after free flowering.In 1947 46 of these plants survived; 43 of them flowered this summer.It could be established that though most of the F2 plants looked like C .epigeios or the original F1 hybrid -C .arundinacea X C .epigeioseight plants showed remarkable similarities to Calamngrostis uaria (SCHRAD.) HOST., a Middle-European-Asiatic species, which in Scandinavia only occurs in the island of Gotland.The chromosome numbers of these eight plants deviated, however, from that of C .uaria.The F2 plants had 2n = 35, 37, or 38, while a true C .uaria from nature has 2n=28.Heredllas XXXIV.