What did the differences in the f1 and f2 offspring show Mendel?

Contrast the offspring in the f1 generation to the offspring of the f2 generation.|||In a cross of (say) tall plants versus short plants, the F1 offspring are all tall, but the F2 offspring include both tall and short offspring (3:1 ratio).





This shows that the F1 generation, although tall, must be carrying some "factor" (gene) for shortness.


Also, the 3:1 ratio is best explained by the idea (Mendel's first law) that individuals contain 2 copies of a gene, and these 2 copies separate when the sex cells are formed.