Fertilisation is the process of fussion of male and female gametes. In plants transfer of pollen grains from stigma to ovary. For this to happen a tube grows out of the pollen grain. The pollen travels through this tube through the style to reach ovary. The pollen tube enters the ovary through an opening called micropyle. Here it releases 2 male gametes in the embryo sac in which one male gamete fuses with one female gamete. This is known as syngamy. The other male gamete fuses with two other polar nuclei. This is known as triple fusion. Syngamy along with triple fusion is defined as double fusion.