Mendel performed an experiments in which he took a tall plant with round seeds and a short plant with wrinkled-seeds. In F1, They were all tall and had round seeds. Tallness and round seeds were thus dominant traits. When, he used these F1 progeny to generate F2 progeny by self-pollination, he found that some F2 progeny were tall plants with round seeds, and some were short plants with wrinkled seeds. At the same time there tall plants, but had wrinkled seeds, while others were short, but had round seeds. Thus, Mendel’s experiments show that the tall/short trait and the round seed/wrinkled seed trait are independently inherited.

By the third law
During dihybrid cross by Mendel, it was observed that when two pairs of traits were considered; each trait expressed independent of the other. Hence, he was able to propose the Law of Independent Assortment which says about independent inheritance of traits.