What are the possible types of pollinations in chasmogamous flowers. Give reasons.

In cleistogamous flowers, there are two types of pollination (Chasmogamy is seen) i.e. self pollination and cross pollination.

$(A)$ Self fertilisation - Autogamy : In this type, pollination is achieved within the same flower. Transfer of pollen grains from the anther to the stigma of the flower. This is seen in both chasmogamous and cleistogamous flowers.

$(B)$ Allogamy (Cross-Pollination) : Transfer of pollen grains from anther to the stigma of a different plant is called cross pollination. It is of two types.

$(i)$ Geitonogamy : Transfer of pollen grains from the stigma of another flower of the same plant. Although geitonogamy is functionally a cross pollination involving a pollinating agent genetically it is similar to autogamy since the pollen grains come from the same plant.

$(ii)$ Xenogamy : Transfer of pollen grains from anther to the stigma of a different plant. This the only type of pollination which during pollination brings genetically different types of pollen grains to the stigma.