Question

In order to obtain the F1 generation, Mendel pollinated a true-breeding, say, tall plant with a true-breeding dwarf plant. But for getting the F2 generation, he simply self-pollinated the tall F1 plants. Why?

Answer 1

Genotype of 50% of the offspring would resemble one parent and the rest
the other parent. All the F1 offsprings of the cross are heterozygous so
allowing self pollination is sufficient to raise F2 offspring. Also he intended
to understand the inheritance of the selected trait over generations.