Abstract: 1.The pollen germination of Sorghum vulgate appeared normal on the stigma of the Oryza sativa, but the pollen tubes grew slowly in the style. Some of the pollen tubes may become enlarged in their tips or sometimes bursting, while others have continued to grow and entered the embryo sacs. 2. The growth rate of the pollen tubes varied widely. A few pollen tubes were observed in the embryo sacs of the materials 2 hours after pollination, but most of them entered the embryo sacs much later. 3. The zygote associated with a paucity of endosperm nuclei was observed in the materials 1 day after pollination. The double fertilization and 8–12-celled proembryo associated with a number of the free nuclei of the endosperm appeared with a rather high frequency (10.3%) in the materials 3 days after pollination. Some of them are normal in appearance and others may show more or less abnormalities. 4. No division figure was found except in one single case in which mitoses have occurred in both the proembryo and the endosperm. It is most likely that in such case the proembryo and the endosperm if left intact might develop further. 5. A 80-celled embryo was the biggest one which appeared in the materials 5 days after pollination. In general, no cells were ever formed in the endosperm, except in one instance among the 7 days materials the endosperm became cellular in micropylar end. In all other cases the endosperm either ceased to develop early or disorganized. The disorganized endosperm materials are considered to be utilized by the embryo. 6. In certain instances the free nuclei of the endosperm were not distributed at random. They were not equal in size and might fuse into giant nuclelei. 7. The most striking feature is that in the embryo sacs, in which double fertilization or proembryo and endosperm have occurred, a dark stained pollen tube was commonly present. This fact leads us to the conviction that in general only if a healthy pollen tube entered the embryo sac, double fertilization can take place and further development can proceed. 8. In certain cases the protoplasm of the embryo cells appeared scanty. It is apparently that the normal metabolism of the embryo was disturbed owing to the lack of nutrient, and the death of the embryo ensued. 9. No differentiated embryo was observed and no mature seeds were produced. The materials fixed 12 days after pollination showed a variety of abnormalities and collapses. The authors believe that the failure of seed production of rice X kaoliang was primarily due to the fact that the pollen tubes in the style grew too slowly to reach the embryo sacs in time. The consequence is that the double fertilization took place only in a late stage while the male and female gametes may have already become unhealthy. In addition, in this late stage the stored starch in the maternal tissues having gradually disappeared, the nutrient supply to the embryo sac was therefore limited and the young embryo and endosperm were finally in starvation.