The process of fertilisation in plants is known as double fertilisation. The ovary has 8 haploid cells 3 antipodal cells, 2 cental polar nuclei, 2 synergids and one egg cell. During the process of fertilisation one haploid sperm fuses with the egg to form the diploid zygote (process known as syngamy) and the other haploid sperm cell fuses with the two haploid polar cells in a process known as triple fusion. So, fusion takes place twice during the process of fertilisation and hence, the process is known as double fertilisation.