There are commonly eight nuclei in the embryo sac: the egg apparatus at the micropylar end, made up of an gee nucleus and two synergid nuclei;

• 胚囊：是存在于显花植物胚珠珠心中的一个大型椭圆状的囊状结构，卵细胞受精和随后的胚胎发育均在这里进行。