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 2nd is between the second male gamete and polar nuclei forming the primary endosperm nucleus. The ploidy of PEN is 3n (male gamete[1n] + polar nuclei [2n]).

Plant chromosome number is $24\mathrm{ }\left(2\mathrm{n}\right)$ . Thus, $\mathrm{n}=\mathrm{ }12$ .

Endosperm is triploid, 3n. Therefore, its chromosome number will be $36$ .