Cytological Studies of Diploid and Triploid Populus Tremula and of Crosses Between Them

I T was stated by BLACKBURN and HARRISON (1924) that the diPlOid.chromosome number is 38 and the haploid number 19 in Populus tremula; these numbers were confirmed by MVNTZING (1936) and (1937).P. tremula has the chromosome number 2 X 19, in common with all other Populus species, about fifteen, the chromosome numbers of which are known (BLACKBURN and HARRISON, 1924;MEURMAN, 1925; WETTSTEIN, 1937;PETO, 1938).The only reported exception has been recorded by BLACKBURN and HARRISON (1924), who consider P. balsamifera to be a tetraploid; MEURMAN found (1925), however, the chromosome number 2x = 19 16015223, 1940, 3-4,