The different stage that leads to the formation of megaspores is known as the megasporogenesis. A single cell from the hypodermal region of the nucellus functions as the archesporial initials which recognized by the larger size, prominent nucleus and dense cytoplasm. In the tenuinucellate type of ovule, the archesporial initials directly functions as the megaspore mother cell. In certain cases the primary sporogeneous cells functions as the megaspore mother cell or the megasporocyte.
The megaspore mother cell is a diploid cell which undergoes reduction division forming the dyad which again divides to form the linear tetrads. All the four haploid cells of the tetrads are known as the megaspores. The megaspore that is lying towards the chalazal end will only remain functional; rest of the three megaspores degenerates. The megaspore is the first cell of megagametophyte.
