Mendel counted 224 white-flowered pea plants in the F2 generation. They appeared after the purple-flowered F1 hybrids were allowed to self-pollinate.
For this experiment, Mendel began with true-breeding pea plants with contrasting flower colors: purple and white. Every plant in the F1 generation had purple flowers, making purple the dominant visible trait and making the white trait appear to have disappeared. The F2 generation showed that it had not been lost; it reappeared when the hybrids reproduced.
Mendel recorded 705 purple-flowered plants and 224 white-flowered plants, for 929 plants in total. The observed ratio was about 3.15 purple to 1 white, close to the theoretical 3:1 phenotype ratio expected when two heterozygous plants are crossed under complete dominance.
The white-flowered plants represented the recessive phenotype. In modern genetic notation, the F1 plants are commonly modeled as heterozygotes, carrying one allele for purple flowers and one for white flowers. The result helped establish the law of segregation.