What was a conclusion that Mendel drew from the F2 generation of this cross?

Answer;

That parental traits that were not observed in the F1 reappeared in the F2.

Explanation; Mendel accounted for the observation that traits which had disappeared in the F1 generation reappeared in the F2 generation by proposing that traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1. It was important that Mendel examined not just the F1 generation in his breeding experiments, but the F2 generation as well, because parental traits that were not observed in the F1 reappeared in the F2.