Pollination is the transfer of pollen from the anther (male organ of the flower) to the stigma (female organ of the flower) of the same or different flower. Fertilization occurs once the pollen grain reaches the stigma, it produces a pollen tube, which grows down through the style to the ovary. The pollen tube expands down the style to the opening of the ovary and deposits the male gamete at the egg. The male and egg each contain half of the genetic material needed to form a zygote which later develops into a new plant.