The flowers appear at the times most suited to the production of seed for the continuation of the species. Before seed can develop the flower must be pollinated. This means that the dust-like pollem produce by the stamen of the flower must be transferred to the stigma of the ovary. Pollination is brought about by various means. Most plants are pollinated by insects and, therefore, flower at the time when the insects are active. The flowers may have evolved a particular colour and scent to attract particular varieties of insects.
Five classes of insects visit flowers Hamiptera (bugs), Caleoptera (beetles), Dipters(flies), Hymenoptera (bees) and Lepidotera (moths and butterflies). Pollination by bird is widespread throughout the tropics and some animals, such as bats, also play a part. Wind pollinated plants include all the conifers, grasses, sedges and rushes, and many forest trees which tend to flower either early or late in the season when the chance of wind is greater. If pollination by some other agent has failed, self-pollination will often take place at the end of a flower’s life. This is usually brought about by movements of the stamens.