Chapter 13, Problem 6GP

In sweet pea plant, an allele for purple flowers $\left(P\right)$ is dominant when paired with a recessive allele for red flowers $\left(p\right)$. An allele for long pollen grains $\left(L\right)$ is dominant when paired with a recessive allele for round pollen grain $\left(l\right)$. Bateson and Punnett crossed a plant having purple flowers/long pollen grains with one having white/flowers/round pollen grains. All $F_1$ offspring had purple flowers and long pollen grains. Among the $F_2$ generation, the researchers observed the following phenotypes:

296 purple flowers/long pollen grains

19 purple flowers/round pollen grains

27 red flowers/long pollen grains

85 red flowers/round pollen grains

What is the best explanation for these results?