Outbreeding devices prevent the occurrence of self-fertilization in plants. The outbreeding devices are as follows:
1. Dioecism: Plant has either the male flowers or the female flowers so that self fertilization never occurs.
2. Dichogamy: It is the process of differential maturation of anther and stigma. When stigma becomes receptive before the anther dehiscence, it is called protogyny. When anther dehisces earlier than stigma becomes receptive, it is called protoandry.
3. Herkogamy: It occurs when stigma and anthers are prevented to come in contact separating the space. Either the style gets longer so that pollen cannot reach the stigma or the style gets shorter so that anther dehisce away from the stigma.