Pollen grains grows pollen tube to the ovule. This tends to be species specific.
The male nucleus travels down the tube to the ovule.
Four things happen:
1.Pollen Nucleus will fertilise the ovule which will lead to the Zygote which will grow into the embryonic plant)
(Pollen nucleus + Ovule ===> Zygote===>Embryonic plant)
2.Outside of the ovule forms the seed coat (TESTA)
3.Formation of Cotelytons (food stores for the seedling that will support the plant until the plant develops its first sets of leaves)
4.Thickening of the walls of the ovary, so the plant will put sugars, protein etc that will build it up, which forms a fruit which is developed from the wall of ovary/carpel.
Here are some examples of fruits and their seeds inside:
Examples of different kinds of seeds:
Fruit on the left and seed on the right: