The PMC(pollen mother cell) meiosis process and pollen morphology of 4 species were observed and the pollen living activity of 2 species was measured. It was discovered that the PMC meiosis process of J. regia, J. mandshurica and J. nigra were basically normal, but that of J. hopeiensis was very irregular. The karyotypes of 7 species were analysed. According to the karyotype and pollen characters, 7 species tested were divided into 3 sections, and they are sect Jglans, sect Cardiocaryon and sect Rhysocaryon. The evolutionary relationships among the sections and the species in one section were approached. The authers pointed out that J. hopeiensis should be regarded as an independence species and the Juglandaceae was probably derived from two different plants with x=8 in phylogeny, and supported the view that China should be one of the original places of J. regia.

Key words: evolution, Juglandaceae, Juglans, karyotype, microsporogenesis, walnut