The ovule or the megasporangium develops as a small protuberance of the placental tissue. In the very young ovule a single hypodermal cell is differentiated as the archesporium. This archesporium cell may or may not cut off some parietal cells and then becomes the megaspore mother cell. The megaspore mother cell now undergoes meiosis or reduction division, and, usually, a linear row of four haploid megaspore cells (linear tetrad) is formed.