Abstract: The development processes of ovule and endosperm, and the relation of embryo and endosperm developments in sexual reproduction for the female inflorescence of thirty-year-old Betula platyphylla were studied. The results showed that the flower of B. platyphylla is syncarpous gynoecium, with 2 styles. The ovary has 2 locules, with 1, 2 ovules or absence of each locule, which is axile placenta, anatropous, unintegmic, and crassinucellate. Suspensor is shorter and consists of 3 cells. From macrogamephyte formation, and embryonal development to the autumn in four months, the ovule undergoes the change of morphological structure and adaptation. At the same time, endosperm plays a main advancing role in the embryonal development, which is nuclear type. And then, the anatomical structures of embryo and endosperm developments, their interrelation, and the each factor of influencing the quality of seed were studied and discussed.

Key words: Betula platyphylla, ovule, embryo, endosperm