To develop a mature female gametophyte, or embryo sac, from a megaspore mother cell in an angiosperm plant, the process involves a sequence of cell divisions. Initially, the megaspore mother cell undergoes one meiotic division. This meiotic division results in the formation of four haploid megaspores. Out of these, typically only one megaspore survives and continues to develop, while the others degenerate.

Following the meiotic division, the surviving megaspore undergoes three successive rounds of mitotic division, without cytokinesis. This series of mitotic divisions leads to the formation of an eight-nucleate structure. Subsequently, these nuclei organize to form a mature female gametophyte, or embryo sac, which is ready for fertilization.

Thus, the complete development from a megaspore mother cell to a mature female gametophyte in an angiosperm plant involves 1 meiotic division followed by 3 mitotic divisions. This sequence ensures the proper formation of the structures necessary for reproduction in flowering plants.