The method of self-pollination in which the stigma of a flower receive pollens from the anther of same flower is known as autogamy. For autogamy both sex organs of a chasmogamous flower should mature at the same time. As chasmogamous flowers open at maturity, pollen release and for the process of autogamy stigma receptivity should be synchronised.
In such flowers, the length of anther and stigma plays secondary role in autogamy. e.g., in case of protandry (pollens nature early) and protogyny (stigma matures early) leads to cross-pollination.