Next Mendel took the pollen from true breeding tall pea plants, and put it on true breeding short plants. He called these true breeding parent plants the P1 generation. He wanted to find out which trait would be passed to the offspring, the trait for being tall, or the trait for being short. What do you think happened?

To his surprise, all of the offspring were tall. Mendel called this second generation of plants the F1 generation. The trait for short stemmed plants seemed to have simply disappeared. Finally, Gregor Mendel took pollen from this F1 generation of pea plants, and put it on other pea plants in the same F1 generation. What do you think happened?

Amazingly, the short stemmed trait reappeared. Some of the offspring were short.