Abstract: Observations were made on the fertilization and early embryo development in intergeneric cross between Avena magna and Avena nuda. The pollen germination of Avena nada appeared to be normal on the stigma of Avena magna and the pollen tubes grew into the style and entered the embryo sacs. In 168 florets fixed after pollination, 2.38% had double fertilization and produced embryo and endosperm, but the endosperm development was slower than that of the embryo, 1.79% had only embryo and 1.19% had only endosperm. The frequency of fertilization and embryo formation were 5.36% and 4.17% respectively. Due to the lack of endosperm or its abnormal development and abortion, no viable seeds were poduced. Cytoembryological evidence was provided for crosses between Avena magna and Avena nuda.