Plants and Insects find "mutual benefit"
Plants also responded to the flying skills of insects by using such mobility for the distribution of the male reproductive cells (pollen). Unlike spores in the lower plants, pollen needs to reach the female cell for the development of more adult plants. Wind-dispersal of pollen which is typical in the pines (Gymnosperms), requires vast quantities of pollen for even moderate pollination success. Alternatively if insects could be used to carry pollen to the female cells by using a small incentive (e.g. food), much less pollen would be required to achieve similar levels of pollination success. Such incentives for insect pollination evolved with the earliest of the flowering plants; the magnolias which appeared about one hundred million years ago. In these plants the egg cells are clustered in the centre, each protected by a green coat with a receptive spike on the top called a stigma with which it receives pollen and is necessary for fertilization. Grouped around the egg cells with their stigmas are stamens which produce the pollen. In order to bring these organs to the notice of insects, the whole structure is surrounded by brightly coloured modified leaves called petals.