Abstract: The structure of the spermtozoid and fertilization process of Ginkgo biloba were studied by light microscopy using paraffin and epoxy resin semi-thin section . It was found that the spermatogenous cell divided to form two semi-spherical sperm cells prior to fertilization. Each sperm cell contained one vacuole-like structure, one blepharoplast and one fibrillogranular body. The two vacuole-like structures from the same spermatogenous cell could be located at the same proximal surface or the same distal surface or the proximal surface and distal surface, respectively. The position change of vacuolelike structure might be caused by the rotation of sperm cells for flagellar movement and indicated that the rotation of the sperm cells could be happen when they were in pollen tube . The nucellus at the micropylar end showed regular changes during fertilization . Fistly , the nucellus protruded upward, then, the fertilization drop appeared, and finally it shrink. These phenomena were good morphological characters to determine the optimal time for fertilization. At the time of fertilization, the integral sperm with flagella entered into the archegonium, and then the sperm cytoplasm and the flagella were left beyond the egg cell , while only the sperm nucleus which was a dark area about 30 μm in diameter entered into the egg cell. The mature sperm nucleus which were about 40μm might be condensed before it entered into the egg cell. These results have some significance in understanding the phylogeny of Ginkgo biloba and reproductive evolution of gymnosperms.

Key words: Ginkgo biloba