(a) : In cleistogamy, as the flowers never open so there is no alternative of self pollination. It is invariably autogamous. In xenogamy, pollination takes between two flowers of different plants (genetically and ecologically). It can ocur by wind, water, insects and animals.Chasmogamy occurs when the flowers expose their mature anther and stigma to the pollinating agents. Geitonogamy is the pollination taking place between the two flowers of the same plant or genetically similar plant. Genetically, it is self pollination but as the agency is involved it is ecologically cross pollination.