Abstract: The fertilization and the development of endosperm and embryo of Populus euphiatica Oliv.have been studied.The results are summarized as follows;1.The stigma is of wet type.The exudate that stained red with Sudan Ⅳ is derived from the glandular stigmatic surface cells.The cuticle gives a clear green fluorescence following auramine O staining,2.48 hours after pollination,two sperm cells are seen in the pollen tube within the ovarian cavity.Each sperm cell contains a large nucleus that is surrounded by cytoplasm.The nucleus is spherical,about 2.5-3.0 μm in diameter,with a prominent nucleolus.3.Fertilization takes place in 8-13 days after pollination.The pollen tube enters the ovule through the micropyle (porogamy).The sperm nucleolus is more distinctive during the fusion of the male and female nuclear membranes.The male and female nucleoli fused together to form a new nucleolus,the fertilized egg nucleolus.4.The endosperm is of nuclear type.Cellularization begins at globular embryo stage and completes its process at heart-shaped embryo stage.The growth curve correlations of the endosperm and embryo show that the nuclear endosperm does not have a significant role in nourishing the proembryo during embryogenesis,but the cellular endosperm do provide nutrition to the developing embryo.5.After resting for 19 days,the zygote divides transversely,resulting in an apical cell and a basal cell.The apical cell divides transversely or longitudinally to form a linear or T-shaped proembryo.Globular embryo stage lasts for 10 days.Growth of the embryo follows the pattern of a typical S-shaped curve.6.Timetable from pollination of the flower to fruit maturity has been given.