Mendel conducted breeding experiments on pea plants :He selected pure breed tall and dwarf plants. $\mathrm{He}$ cross pollinated these plants. In the $\mathrm{F}_1$ generation obtained only tall plants, tallness is the dominant trait.Then, he produced $\mathrm{F}_2$ generation by selfing of hybrids of $\mathrm{F}_1$ generation. He found that $\frac{3}{4}$ th of the plants were tall and $\frac{1}{4}$ th were dwarf. The trait which remains hidden in $\mathrm{F}_1$ generation plants is the recessive trait.