Flowering plants have developed many devices to discourage self-pollination and to encourage cross-pollination. Explain three such devices.

Explanation

See Q.11, Set-II., Outside Delhi-2015. and see also for third devices :
The third device to prevent self pollination is self-incompatibility. Its is a genetic mechanism and prevents self-pollen from fertilising the ovules by preventing pollen germination or pollen tube growth in the pistil.