Polygonum type of embryo sac/female gametophyte of angiosperms is

Polygonum type of embryo sac/female gametophyte of angiosperms is 7-celled, 8-nucleate.
The mitotic division (reduction division) of the mother megaspore gives rise to female gametophytes. The megaspore divides mitotically thrice to form firstly 2 then 4 and out of these 4 forms 8 nucleate embryo sacs. The process of formation of the 7-celled, 8-nucleate nature of female gametophyte.