Fertilisation by pollen from another flower
Cross-pollination (or cross-fertilisation or allogamy) describes the fertilisation of a flower by pollen originating from another flower. The term is used in contrast to autogamy in which the flower pollinates itself. There exist two kinds of cross-pollination: geitonogamy (the flower is fertilised by pollen of another flower of the same plant) and xenogamy (the flower is fertilised by pollen of another plant). Some plant species have developed natural mechanisms to avoid autogamy.