Here's why:

* Pollen Tube: This is a tube that grows from a pollen grain after it lands on the stigma of a flower.

* Sperm: The pollen grain contains two sperm cells.

* Fertilization: One sperm cell travels down the pollen tube and fertilizes the egg cell within the ovule of the pistil, leading to the formation of a seed.

Let me know if you have any other questions about plant reproduction!