In corn, a nucleus from the male gametophyte fuses with two nuclei from the female gametophyte. It gives rise to a triploid cell, 3n, which replicates to form the endosperm. The nutritive tissue surrounds the embryo.
The table shows the genotypes of endosperm:
| Female | Male | Polar nuclei ? | Sperm ? | Endosperm-3 n |
| s/s | S/S | s and s | S | S/s/s |
| S/S | s/s | S and S | s | S/S/s |
| S/s | S/s | 1/2S and S | 1/2S | 1/4S/S/S |
| 1/4S/S/s | ||||
| 1/2s and s | 1/2s | 1/4S/s/s | ||
| 1/4s/s/s |