According to the law of dominance, a trait is represented by two contrasting factors of a gene in a heterozygous individual; the allele/factor that can express itself in a heterozygous individual is called as a dominant trait. The other factor whose effect is masked by the presence of dominant factor is called recessive factor. A cross between two pure breeding tall (TT) and dwarf (tt) varieties gives all heterozygous tall (Tt) $$F_1$$ progeny. Selfing of $$F_1$$ hybrid gives tall and dwarf progeny in 3:1 ratio. The recessive factor is present in $$F_1$$ hybrid but is masked by a factor for the dominant trait and that’s why it produced both parental types in $$F_2$$ progeny.