How do Mendel's experiments show that traits may be dominant or recessive?

Mendel selected true-breeding tall $(TT)$ and dwarf $(tt)$ pea plants.
He crossed these two plants to obtain the first filial or $F_1$ generation.
All the $F_1$ plants obtained were tall.
Then,Mendel self-pollinated the $F_1$ plants and observed that not all plants in the $F_2$ generation were tall; one-fourth of the $F_2$ plants were short.
From this experiment,Mendel concluded that the $F_1$ tall plants were not true-breeding.
They carried traits for both short and tall height.
They appeared tall only because the tall trait is dominant over the dwarf trait,which is recessive.