Abstract:The large-seeded longan (Dimocarpus longan Lour.) cultivar ‘Jiuyuewu’and abortive-seeded cultivars, ‘Minjiao 64-1’,‘Minjiao 64-2’and ‘Baihe’were conducted to inbred or hybrid by artificial pollination, their growth of pollen tube was observed, and the female gametophyte and early zygotic embryo development of two cultivars were investigated by serial paraffin section technique. The results showed that ovule abortion of longan occurred before formation of the mono-nucleated embryo sac, and the abortive rate of ovule in abortive-seeded cultivars were obviously higher than that in large-seeded ones. Pollination rates had difference among different hybrid combinations. Nevertheless, a pollen tube could be observed entering the embryo sac in all combinations tested after pollination 36 to 48 hours. Embryo of abortive-seeded cultivars began to abort 10 days after flowering, which abortion rate was obviously higher than that of large-seeded cultivar. Ovaries did not develop until fertilization occurred. Pistils with abortive ovules did not enlarge 10 days after flowering, and did not develop to abortive-seeded fruits. Early embryo abortion occurring at 10 to 30 days after flowering could be the main factor to form abortive-seeded fruits. The endosperms in abortive-seeded cultivar ‘Baihe’could develop to embryo. The chalazal end cells, synergids and endosperms occurred abnormal development in about 24% ovules of ‘Minjiao 64-1’in ovule development process, which might relate to early embryo abortion.