How do Mendel's experiments show that the traits are inherited independently??

Mendel carried out dihybrid crosses by crossing two pea plants differing in contrasting traits of two characters. 

For example he crossed a pea plant having yellow coloured and round seed with another pea plant bearing green coloured and wrinkled seed. In the F2 generation, he got the pea plants with two parental and two recombinant phenotypes as yellow round and green wrinkled (parental) and yellow wrinkled and green round (recombinant). This indicated that traits separated from their original parental combinations and got inherited independently.