In the common angiosperm arrangement, one sperm fuses with the ovum to form a diploid zygote; another fuses with the central biological cell's two polar cell nuclei, initiating endosperm with three chromosome sets. The zygote develops into a plant embryo, and the ovule develops into a seed.[ref]
For an original counting example, stipulate a plant with chromosomes and the common two-polar-nucleus arrangement. Each haploid sperm and ovum contributes . The zygote therefore has chromosomes, while the initiating endosperm cell nucleus has . The maternal seed coat remains derived from plant tissue; the whole seed has no single uniform chromosome count. This is bookkeeping for a stipulated example, not identification of a particular species. It follows by counting the chromosome sets entering each fusion, rather than assigning one count to everything enclosed by a seed coat.
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