Explanation

During microsporogenesis, the sporogeneous cells may directly acts as microspore mother cells or pollen mother cells or PMCs. Each PMC, by a meiotic division, gives rise to a group of four haploid microspores, which are combinedly referred to as microspore tetrad. The first mitotic division in a pollen grain or microspore results into two unequal cels. The large is the vegetative cell, which eventually forms the pollen tube. The smaller one is the generative cells which produce the male gametophyte by another mitosis.