Plants have specific adaptations or so-called contrivances for both autogamy and allogamy.
Some contrivances for autogamy (self-pollination) are:
1. Formation of bisexual flowers (Monocliny) ensures self-pollination. When both sexes are present in the flower, and if they are maturing at the same time, the flower is preferred for autogamy.
2. In a bisexual flower, when both sexes mature at the same time (Homogamy), it goes for self-pollination. Example-Pea, Argemone.
3. Some flowers, as in case of Commelina, Oxalis, etc. never open. Such flowers are called Cleistogamous flowers. They operate self-pollination, as the flowers are not available for any pollinator.
4. In a flower which is normally opening (Chasmogamous), the androecium and gynoecium are brought nearer to each other to proceed for self-pollination only.
5. Some plants, like wheat, pea, are pollinated before anthesis (Bud pollination). This ensures cross-pollination, once the flower is open, is not possible at all.
6. In plants like Argemone, the anthers are epipetalous. During the sleep movement, the anthers are brought nearer to stigma to ensure self-pollination.