Xenogamy is transfer of pollen grains from anthers of one plant to stigma of a different plant which, during pollination, brings genetically different types of pollen grains to stigma.Geitonogamy is the transfer of pollen grains from anther of a flower to the stigma of another flower on the same plant.Cleistogamy means the formation of flowers that do not open (CL), and thus production of seeds is a result of autogamy.