Heredity: Mendel's Explanation

Gregor Mendel observed that the first generation of pea plants had no short plants, while the second generation had about 1/4 short plants. He used his mathematical background to hypothesize that each plant has two factors for each trait, with one factor contributed by each parent. Mendel suggested that some factors can mask others, such as tall height dominating short height. These factors are now known as genes.

What does Mendel's reasoning suggest about the relationship between traits and factors?

In Mendel's experiments, which trait was observed to mask the other in pea plants?