When Mendel self-pollinated the tall F1 plant he observed:

Mendel self-pollinated the tall F1 plants and to his surprise found that in the F2 generation some of the offspring were ‘dwarf ’; the character that was not seen in the F1 generation was now expressed. The proportion of plants that were dwarf were 1/4th of the F2 plants while 3/4th of the F2 plants were tall. The tall and dwarf traits were identical to their parental type and did not show any blending, that is all the offspring were either tall or dwarf, none were of in between height.