The pollen nucleus fuses with the egg in the ovule
The pollen nucleus that travels down the pollen tube then fuses with the egg inside the ovule.
The car crashes into the cart being pulled by a mule (ovule) which was packed full of eggs (egg). The collision causes a real mess but they all refuse (fuse) to clean it up.
When the pollen tube has entered the ovary the pollen nucleus from the pollen grain travels down the pollen tube into the ovule and fertilises the egg within it.
The egg is fertilised
When the egg has been fertilised it becomes a seed. The food store of the seed provides the energy the embryo needs to germinate and continue to grow.