Abstract:By using the technology of GMA half-section the comparative studies on the structure of embryo sac between polyembryonic rice strain AP IV and haploembryonic rice cuhivar “IR36” showed: In AP IV, except 7.8% of ovaries in which the embryo sac degenerated, there were only 27.1% of ovaries in which the structure of embryo sac was similar to that of "IR36‘ which was of the Polygonum type; 65.1 % of ovaries were different from “IR36”, in which some changes happened in the embryo sac: Of most two kinds of variant embryo sac, referred as poly-egg apparatus embryo sac (53.3%) and double set of embryo sac (6.3%) were found. In the poly-egg apparatus embryo sac, three egg-apparatuses were the majority which could be further divided into three types, namely, 5-2-1 type, 6-2-0 type and 5-3-0 type, based on the whole structure of embryo sac. The double set of embryo sac characterized with a large embryo sac inlaid with a small embryo sac, and with the eggs far from the micropyle part. Moreover, the other variants were also found. According to the analysis, genetic polymorphism of the structure of embryo sac was found in single-panicle in AP Ⅳ.