Assertion (A) is false, and Reason (R) is the correct.

Assertion (A) is true. Geitonogamy is indeed a form of pollination where pollen transfer occurs between two different flowers on the same plant. Functionally, it involves cross-pollination because it involves the transfer of pollen from the anther to the stigma of a flower. However, genetically, it results in self-pollination because the pollen and ovules come from the same genetic individual (plant). 
Reason (R) is also true. The statement accurately explains geitonogamy, where pollen transfer occurs between flowers of the same plant. This process ensures genetic continuity within the same plant, leading to self-pollination genetically.