Mendel took pea plants with contrasting characteristics which included tall plant and dwarf (or short) plant. On cross pollination, he found all tall plants in the first generation \( F_1 \) and further by the self pollination of \( F_1 \) tall plants, he found that the plants of the second generation consisted of tall and short pants in the ratio of 3 : 1. On the basis of these experiments, the characteristics that appeared in the first generation were called dominant (i.e. tall plants) and the characteristics that did not appear were called recessive (i.e. dwarf plants).