Is it ensure, insure, or assure?
The transfer of pollen from the male reproductive organ (an anther or a male cone) of one plant to the female reproductive organ (a stigma or a female cone) of another plant. Insects and wind are the main agents of cross-pollination. Most plants reproduce by cross-pollination, which increases the genetic diversity of a population (increases the number of heterozygous individuals). Mechanisms that promote cross-pollination include having male flowers on one plant and female flowers on another, having pollen mature before the stigmas on the same plant are chemically receptive to being pollinated, and having anatomical arrangements (such as stigmas that are taller than anthers) that make self-pollination less likely.