Principle of Dominance When Mendel crossed the pollen from a purple flower onto a white flower, he found that all of the seeds produced offspring with purple flowers. He concluded that some traits were dominant over other (recessive) traits. He determined that dominant traits appear more often. When Mendel crossed the pollen from a plant with green pods with a plant with yellow seed pods, all of the offspring had green seed pods. This told him that (Type here) seed pods were dominant over (Type here). seed pods.