In the anthers of each stamen there are pollen sacs. Within the pollen sacs there are microspore mother cells, or microsporocytes. These cells undergo meiosis forming microspores. Each microspore by mitosis forms a pollen grain containing one generative cell and one tube cell. The pollen grain is the male gametophyte.
When pollination occurs and the pollen grain makes contact with the stigma (the apex of the pistil) the tube cell elongates its cytoplasm forming the pollen tube that grows towards the ovary. The generative cell divides forming two sperm nuclei (male gametes) that migrate through the pollen tube.
