Pollen grains are formed from the anther of a stamen of a flowering plant. There are pollen sacs inside the anther. At the adult stage, pollen mother cells (2n) inside the pollen sacs produce four pollen spores (n) through meiosis from each.
Characteristics of a pollen spore (n):
i) Pollen spores are haploid and round in shapes.
ii) It is surrounded by two coverings of which the outer thick covering is called Exine and the inner layer is called Intine.
iii) There is a round pore inside the germ pore of exine.