By using the laser scanning confocal microscope and plastic (Leica 7022 historesin embedding kit) semi-thin sectioning technique, comparative studies on the development of endosperm were carried out between autotetraploid and diploid rices About one third of the ovaries in the autotetraploid showed normal endosperm development as those in the diploid. In these ovaries, one of the polar nuclei would fuse with the sperm nucleus, and the primary endosperm nucleus formed and underwent the first division in 4 hours after pollination; the anticlinal wall began to grow centripetally between the free nuclei starting from the wall ingrowths of the embryo sac near the micropylar end, and some of the phragmoplasts formed transformed into periclinal walls. In addition, some of the cell wall situated in the middle of the endosperm appeared to originate from phragmoplasts, whereas others seemed to develop randomly without the obvious formation of phragmoplasts Cellulose began to accumulate in the wall of aleurone cell layer at 6 days after pollination. The cellulose wall of the cells of the aleurone cell layer appeared to have completely formed within 7 to 8 days after pollination On the other hand, about two thirds of the ovaries in the autotetraploid showed abnormality in endosperm development with various types, such as non-fertilization, abnormal fertilization, endosperm development-delay and non-synchronization in the development of cellulose wall of cells of the aleurone layer These abnormalities usually resulted in decreased seed setting in autotetraploid rice. By using the laser scanning confocal microscope and plastic (Leica 7022 historesin embedding kit) semi-thin sectioning technique, comparative studies on the development of endosperm were carried out between autotetraploid and diploid rices about one third of the ovaries in the autotetraploid showed normal endosperm development as those in the diploid. In these ovaries, one of the polar nuclei would fuse with the sperm nucleus, and the primary endosperm nucleus formed and underwent the first division in 4 hours after pollination; the anticlinal wall began to grow centripetally between the free nuclei starting from the wall ingrowths of the embryo sac near the micropylar end, and some of the phragmoplasts formed of into micropicrillar end, and some of the phragmoplasts formed in into the periclinal walls. develop randomly without the obvious formation of phragmoplasts Cellulose began to accumulate in the wa ll of aleurone cell layer at 6 days after pollination. The cellulose wall of the cells of the aleurone cell layer had to formed completely within 7 to 8 days after pollination On the other hand, about two thirds of the ovaries in the autotetraploid show abnormality in endosperm development with various types, such as non-fertilization, abnormal fertilization, endosperm development-delay and non-synchronization in the development of cellulose wall of cells of the aleurone layer These abnormalities usually resulted in decreased seed setting in autotetraploid rice.