Cross-pollination
The process by which the mature pollen of a flower is deposited on the stigma of a flower of the same plant, or of another plant of the same species, is called cross-pollination.
Figure to be added
Cross-pollination allows the characteristics of two plants to be mixed. This helps in producing a strong new generation carrying new characteristics.
This is why the adaptations exist
Because of this, some flowers have become adapted to avoid self-pollination and carry out cross-pollination instead. The next page sets out five such adaptations — and every one of them is a way of making the flower's own pollen useless to its own stigma.
The same trade-off, once more
Self-pollination is certain and produces sameness. Cross-pollination is chancy — it needs an agent and a second flower — and produces variety. This is the asexual-against-sexual trade-off from table 14.1 appearing again, one level down, within sexual reproduction.