In order for a flower to produce fruits with seeds, the pollen from one flower has to be carried to another flower
Flowering plants reproduce with sexual parts contained in a flower. Actually, the flower itself exists for the sole purpose of reproduction. When it blooms, it contains male parts and/or female parts. The female parts contain eggs, which sit in an ovary at the base of the pistil. At the top of the pistil is the stigma, which catches pollen. The male parts of a flower produce sperm, which is contained in pollen. Pollen is made in the anther which sits at the top of the stamen of the flower. With stamen and pistil ready, a flower awaits pollination, the end result of which will be seed and fruit.
Pollination
Pollination is accomplished with either wind power or the help of creatures that the flower attracts by virtue of color, markings, scent and nectar. When creatures such as birds, bees and bats visit a flower, they pick up pollen. When the creatures visit other flowers, the pollen is deposited onto the stigma so that fertilization can take place. Smallish, non-showy flowers are those that rely on wind to blow pollen to the stigma.
Double Fertilization
Flowers are unique in their use of double fertilization to accomplish reproduction. First a tube grows from the pollen down into the pistil until it reaches the ovary. Once there, one sperm fuses with the egg and begins developing into an embryonic plant. Meanwhile, another sperm fuses with nuclei inside the embryonic sac to create endosperm.
Seed and Fruit
While the plant embryo is developing, the endosperm cells divide repeatedly. Eventually, the endosperm encloses the embryo. Together they form the seed, the endosperm there to provide the food energy the future plant will need as it awakens to emerge from the seed. The ovary, meanwhile, begins swelling around the seed or seeds, becoming the fruit of a flower. In some plants, the floral tube develops into a fleshy appendage around the ripened ovary, as is the case with apples. The core surrounding the seeds in an apple is the ovary wall. In fruit like peas, the pod is the ovary wall.