Pollen is a powder which contains the male gametophyte of seed plants. A pollen grain contains the male gametophyte within the pollen wall, which is composed of sporopollenin. The pollen wall protects the pollen grain during its movement. Once the pollen reaches a part of a seed plant that contains ovules, pollination has occurred. After pollination, germination follows and a tube is created through which the sperm will be delivered to the ovule.