The assertion is correct. Autogamy refers to the transfer of pollen grains from an anther to the stigma of the same flower on the same plant. It is a form of self-pollination where the reproductive organs within a single flower are involved in the pollination process.

On the other hand, the reason is also correct. Xenogamy actually refers to pollination between two flowers on different plants, typically of the same species. It involves the transfer of pollen from the anther of one plant to the stigma of another plant. Xenogamy promotes genetic diversity within plant populations as it brings together genetic material from different individuals.

So, while the assertion is accurate, the reason provided is not a valid explanation for it.