Parts of the Flower
Flowering plants reproduce sexually, with the flower being the reproductive structure of the plant. The flower has four parts: The calyx, which is made up of sepals; the corolla, which is composed of flower petals; the androecium, which are the male reproductive organs (called the stamen and anthers); and the gynoecium (female reproductive organs; individual units are called pistils). Each part of the flower plays a vital role in the reproduction process.
The sepals protect the flower until it is ready to bloom. Inside each anther in the center of the flower lie four pollen sacs. When the pollen is mature, the anther will split open, releasing pollen onto the stamen. The stamen surround the pistil of the flower, which house the female reproductive organs. The pistil contains the stigma, which in turn contains carpels, or ovaries.
Insects are lured to the flower by the brightly colored petals and promise of nectar. When they land on the stamen in the flower, they often transfer pollen grains from the stamen to the sticky surface of the stigma. The wind can also transfer pollen grains. If the transfer of pollen from the stamen to the stigma happens on the same flower, this is called self-pollination. If the transfer happens between two flowers that are the same species, it is called cross-pollination.
When a pollen grain lands on a stigma, travels down the hollow tube and fertilizes the ovule that lies at the bottom of the stigma. The ovule develops into a seed. The carpel surrounding the ovule develops into fruit.
The seeds are then dispersed in various ways. The wind can disperse seeds. Some seeds have hooks on them that cling to animals and even people, which allows them to move from place to place. Other seeds are dispersed when birds or other animals eat the fruit and void the seeds.