(a) 1.Pollens release and stigma receptivity is not synchronised.
2.Anther and stigma are placed at differnt positions so that the pollen cannot come in contact with the stigma on the same flower.
4.Production of unisexual flower.
(b)The transfer of pollen grains from the anther to the stigma of another flower of the same plant is called geitonogamy. Although geitonogamy is functionally cross pollination involving a pollinating agent,genetically it is similar to autogamy since the pollen grains come from the same plant.