- the formation and development of megaspores.
- The formation of megaspores inside the ovules of seed plants. A diploid cell in the ovule, called a megasporocyte or a megaspore mother cell, undergoes meiosis and gives rise to four haploid megaspores. In most plants, only one of the megaspores then goes on to develop into a megagametophyte within the ovule, while the other three disintegrate. In the ovules of angiosperms, megasporogenesis takes place within a structure called a nucellus, and it is the megaspore farthest from the micropyle of the ovary that survives.