Pollen grains ofPicea orientalis, P. sitchensis, Tsuga heterophylla,andT. mertensianawere investigated by means of light, scanning electron, and transmission electron microscopy. The fine structure of these four species, the siamese pollen inP. sitchensis,and the variations in sacci ofT. mertensianawere demonstrated. Pollen morphology ofT. mertensianadiffered from that ofPicea,and even more fromT. heterophylla.The difference in morphology ofTsugaspecies may have been due to varying rates of evolutionary change, to the modification of reproductive structure for their continued existence, or to introgression. From the differences in pollen morphology, the authors consider that the twoTsugaspecies could be assigned to separate genera.