autogamy is self-pollination within the same flower, while geitonogamy involves the transfer of pollen to another flower on the same plant . In monoecious plants like castor and maize, where male and female flowers are on the same plant, autogamy is prevented but geitonogamy is not . However, in dioecious plants like papaya, male and female flowers are present on entirely different plants; this condition successfully prevents both autogamy and geitonogamy .