(i) Pollen release and stigma receptivity is not synchronised.
(ii) Anther and stigma are placed at different position.
(iii) Self-incompatibility.
(iv) Production of unisexual flowers.
Detailed Answer:
Three outbreeding devices are :
(i) Dichogamy : Stamens and carpels do not mature at the same time. Therefore stigma is not receptive at the time of pollen release or vice-versa.
(ii) Dicliny : The flowers are unisexual.
(iii) Herkogamy : There is a physical barrier present between anther and stigma e.g. in calotropis or the anther and stigma are placed in different positions.
