The anther is the pollen producing structure of flowering plants that is found in the male reproductive organ known as the stamen. Often referred to as the pollen sac, anthers are bi-lobed structures that typically rest atop long slender stalks called filaments. The anthers are comprised of tissues that contain spore-producing cells called microsporocytes. These 'pollen mother cells' divide by meiosis to develop into grains of pollen. Each of the many released minute pollen grains contains two male gametes that carry one half of the chromosomes characteristic of the parent plant. For pollination to occur, pollen grains must be transported from the male reproductive organ to the female reproductive organ and usually travel by means of insects, wind, and water.