The pollen grain has a hard outer covering which is known as exine. It is made up of sporopollenin which is the hardest material known and it cannot be degraded by chemical or any other means. On this exine of the pollen grain, there is a small pore which is known as the germ pore. From here the pollen tube arises and help in the transfer of the male gamete from to the ovule. Therefore germ pore is essential during fertilization.