Unisexuality of flowers prevents

Step-by-step solution

The transfer of pollen from anther to stigma is called pollination. Autogamy also called self-pollination involves the transfer of pollen grains of one flower to the stigma of same flower. Self-pollination occurs only in bisexual or hermaphrodite flowers. Geitonogamy involves the transfer of pollen grains from a male flower to stigma of female flower of same plant Thus, geitonogamy operates only in monoecious plants, ie, the plants having male and female flowers on different places. Allogamy or xenogamy also known