In Mendel's F2 generation, the ratio of dominant to recessive phenotypes was 3:1.

Here's why:

* F1 Generation: Mendel crossed homozygous dominant (PP) and homozygous recessive (pp) parents, resulting in all heterozygous (Pp) offspring in the F1 generation. All F1 plants expressed the dominant phenotype.

* F2 Generation: When Mendel self-pollinated the F1 plants, the following combinations were possible in the F2 generation:

* PP: Dominant phenotype

* Pp: Dominant phenotype

* pP: Dominant phenotype

* pp: Recessive phenotype

This resulted in a 3:1 ratio of dominant to recessive phenotypes.