Pollination is the process of mating in plants; it is the precursor to double fertilization. In flowers, pollen is delivered to the stigma through a wide range of mechanisms that ensure an appropriate balance in the genetic make-up of the species. In brassicas, pollen is distributed by bees and other insects. The flower is the device by which the plant recruits the bee. Bees and brassicas have evolved an interdependent relationship.