Double fertilization is a unique characteristic observed in the Angiosperm group of plants. In this, two fertilizations are observed - $1^{\mathrm{s}\mathrm{t}}$ between the female and male gametic cells forming zygote and $2^{\mathrm{n}\mathrm{d}}$ is between the second male gamete and polar nuclei forming the primary endosperm nucleus. The ploidy of PEN is 3n (male gamete $\left[1\mathrm{n}\right]\mathrm{ }+$ polar nuclei $\left[2\mathrm{n}\right]$ ).