Flowers are the reproductive parts of a plant and house the structures that make sex cells. Pollen is the male sex cell in the plant, which is product by the anther portion of the stamen. Ovules, or eggs, are the female sex cells of plants and are produced in the ovary portion of the pistil.
In order for fertilization to occur, plants must transfer pollen from the anther in the stamen to the style in the pistil in a process called pollination. Pollination can occur in a variety of ways, including wind, insects, birds, and even humans. The busiest of the pollinating animals is the honey bee.
After pollination, the pollen grains germinate on the stigma creating a path to the ovary, called a pollen tube.
As the pollen tube completes growth toward the ovule, the grain of pollen divides to form two sperm nuclei. The sperm nuclei travel down the pollen tube and into the ovary.
In a process called double fertilization, one sperm nucleus unites with the egg to form a zygote.
The other sperm nucleus fuses with the two polar nuclei to form the endosperm. After fertilization, the ovule becomes the seed and the endosperm becomes the fruit.