(a) : Some plants such as Viola (common pansy), Oxalis, and Commelina produce two types of flowers­ chasmogamous flowers which are similar to flowers of other species with exposed anthers and stigma, and cleistogamous flowers which do not open at all. In such flowers, the anthers and stigma lie close to each other. When anthers dehisce in the flower buds, pollen grains come in contact with the stigma to effect pollination. Thus, cleistogamous flowers are invariably autogamous as there is no chance of cross­pollen landing on the stigma. Cleistogamous flowers produce assured seed­set even in the absence of pollinators.