Using appropriate terminology, explain the incomplete dominance in crossed true breeding strains of antirrhinum majus?

Antirrhinum majus is the scientific name of the plant more commonly known as a snapdragon. Snapdragons, like Four O'Clock plants, come in a variety of colors, and a large part of that color variety is due to the fact that the gene for flower color shows incomplete dominance.
Incomplete dominance is when an allele for a particular trait isn't completely dominant over the other trait. The result is a trait that appears to be a blend of the other two traits. Let's look at normal dominance to start. A parent that is homozygous dominant for producing red flowers has both dominant alleles. We would write this genotype as RR. A parent that is homozygous recessive for this trait produces white flowers and has a genotype of rr. If those two plants are crossed, all of the possible offspring are heterozygous (Rr). Phenotypically, all of these flowers are also red because the dominant allele is present.
Incomplete dominance introduces a third possible phenotypic trait because the allele isn't completely dominant. A purebred, red snapdragon is genotypically RR, and a purebred white is rr. When those two plants are crossed, the offspring are all heterozygous for flower color. Genotypically, they are Rr; however, a new blended phenotype has been introduced in the F1 generation. The flowers are pink.
The F2 generation is where things get interesting with incomplete dominance. If two flowers from the F1 generation are crossed (Rr x Rr), then the resulting cross produces one RR, two Rr, and one rr. This means that a pair of pink parents can produce red flowers, pink flowers, and white flowers.
http://www.geneticsrus.org/Genes/exceptions.php