The transference of the pollen from the anther to the receptive stigma, whether of the same flower or of a different flower, is known as pollination.
As the pollen is not capable of locomotion, this process either involves some agent for this transference or the anther must be placed in the flower right above the stigma so that pollens may drop directly on the stigma.
If the stigma is pollinated by the pollen of the same flower, it is a case of self-pollination. When the pollen of one flower pollinates the stigma of a different flower but on the same plant, it is called geitonogamy.
Pollination may be affected by different agencies such as wind, water, animals and insects. Accordingly, the types of pollination are:
(i) Anemophily (Wind-Pollinated):
These flowers are inconspicuous and not showy. They are devoid of scent, nectar, etc. They produce a very large quantity of dusty pollens which are light in weight so that they may be carried to longer distances to reach the stigma.
(ii) Hydrophily (Water-Pollinated):
The water plants generally have their flowers above water and are adapted for wind or insect pollination, e.g., lotus. In case of the plants submerged under water, the flowers are small and inconspicuous. The male flowers are small and numerous, they become detached from the plant and float about on the water and approach female flowers. Some of the pollen grains are thus transferred to the stigma.
(iii) Zoophily (Animal-Pollinated):
These flowers are pollinated by birds, bats and other animals and may be of the following types:
(a) Ornithophily (Bird-Pollinated):
Bird- pollinated flowers are not many in number. Tiny birds like humming-birds and honey-thrushers feed on the nectar of flowers like Bignonia and thereby pollinate them.
(b) Chiropteriphily (Bat-Pollinated):
Bauhinia of Java, Epertua and a few other trees are known to be pollinated by bats.
(c) Malacophily (Slug and Snail-Pollinated):
Snails and slugs visit certain flowers and may have a role in their pollination.
(iv) Entomophily (Insect-Pollinated):
The majority of flowers are insect pollinated. Insect pollinated flowers are made attractive to insects in different ways. The pollens are sticky with a rough surface so that they may easily stick to insect limbs. The stigma is also sticky and thus receives the pollens more easily, e.g., salvia, mango, sunflower, jasmine, lady of the night and poppy.