The assertion is incorrect, and the reasoning provided is also incorrect.

Geitonogamy is a type of pollination where pollen is transferred from the anther of one flower to the stigma of another flower on the same plant. It is a form of self-pollination because the pollen grains come from a different flower on the same plant, not from another plant. In geitonogamy, the pollinating agent (such as wind, insects, or other animals) facilitates the transfer of pollen between flowers on the same plant.

Genetically, geitonogamy is not similar to autogamy. Autogamy refers to self-pollination, where pollen is transferred from the anther to the stigma of the same flower. In autogamy, there is no involvement of external pollinating agents, and the pollen grains come from the same flower, ensuring genetic similarity.

In geitonogamy, although the pollen is transferred between flowers on the same plant, it can still result in some degree of genetic diversity because the pollen from one flower may differ genetically from the ovules of the other flower. However, it is not as genetically diverse as cross-pollination, where pollen is transferred between flowers on different plants.

To summarize, geitonogamy is a form of self-pollination involving the transfer of pollen between flowers on the same plant, and it is not functionally cross-pollination. The genetically different types of pollen grains come from different flowers on the same plant, not from another plant.