Embryo sac is female gametophyte of angiosperm which is formed by mitosis in megaspore which is formed by reductional division in megaspore mother cell. Megaspore undergoes three mitosis to form most common type of embryo sac, which is 7- celled and 8 - nucleated structure. Embryo sac consists of 3 cells towards chalazal end known as antipodals, large cell in center known as central cell and egg apparatus towards micropylar end, having one egg cell and 2 synergids. Synergid consists of filliform apparatus.