The primary sporogentous cells of anther divide and redivide mitoticaly to form a mass of sporogenous tissue. The cells of sporogenous tissue act as microspore mother cells or pollen mother cells, which undergo meiosis to form haploid pollen grains or microspores. Pollen grain is the first cell of male gametophyte. A mature pollen is double layered, the outer wall called exine and the inner inline. The nucleus of pollen divide to produce vegetative and generative cell. The generative cell again divide mitolicaly to form two male gametes. The male gamete fertilize the female gamete. As a result of fertilization the zygote is formed, which undergoes rest. The zygote divide and redivide mitotically to form embryo.