Abstract: The embryonic development following P. simonii Cart. × P. pyramidalis Borkh. is described in the present paper. The majority of pollen grains of P. pyramidalis Borkh. may germinate on the stigma of P. simonii Cam and the pollen tubes grow normally through the style and enter the embryo sac from the micropyle. Fertilization occurs as usual 4–7 days after pollination. A lot of proembryos and heart-shaped embryos are abortive; however, the others may develop normally and grow into mature embryos. Some of the endosperms appear normal and others may degenerate at free nuclear stage or cease to develop further at cellular stage. The ovules containg immature hybrid embryos of 19 days, 22 days, 26 days and 29 days after pollination at various developmental stages (heart-shaped stage, torpedo-stage and cotyledonary elongation stage) are excised and inoculated on nutrient agar for culture. The results show that: ( 1 ) Mll0 medium ( 1/2 MS+IAA 0.01 mg/L+BA 0.1 mg/L+sucrose 2% ) is the best of all the media used; (2) immature hybrid embryos of various developmental stages contained in ovules cultured in vitro may grow into normal plantlets.