Flowers can be of two types i.e. chasmogamous flowers or cleistogamous flowers. Chasmogamous flowers are open flowers which have their anthers and stigma exposed. These flowers facilitate cross-pollination. On the other hand, cleistogamous flowers are closed flowers whose anthers and stigmas are not exposed. Since these flowers do not open at all, only self-pollination occurs in these and cross-pollination is never seen. Thus. cross-pollination cannot occur in cleistogamous flowers.