s: Three successive mitotic divisions form it in the megaspore nucleus (or
female gametophyte). The nucleus itself divides into two nuclei which move to
opposite poles to form two nuclei of the embryo sac. The 8-nucleate stage of the
embryo sac is formed after two more sequential mitotic nuclear divisions. A
typical female gametophyte or embryo sac is formed after the 8-nucleate stage.
The antipodal and micropylar end of each of the eight nuclei comprises the six
nuclei grouped. There are two synergids and an egg cell at the center of the egg
apparatus. The polar nuclei are located within the large central cell of the embryo
sac just below the egg apparatus. A typical female gametophyte comprises seven
cells with eight nuclei as both polar nuclei are present within the same cell.