In order to obtain the `F_(1)`-generation Mendel pollinated a pure-breeding tall plant with a pure-breeding dwarf plant. But for getting the `F_(2)`-generatin, he simply self-pollinated the tall `F_(1)` plants. Why?

Explanation

Genotype of 50% of the offspring would resemble one parent and the rest the other parent. All the `F_1` offsprings of the cross are heterozygous so allowing self pollination is sufficient to raise `F_2` offspring. Also he intended to understand the inheritance of the selected trait over generations.