Flowers are complex organs on plants with the purpose of sexual reproduction, the fusing of male and female gametes to form a seed. The male flower part is the stamen and the female part the pistil. Wind, animal or insect facilitates pollination, bringing the male pollen to the female ovary. The petals act to attract pollinators or to protect the sex organs.
The flower parts not directly involved in reproduction are dubbed the perianth, or accessory organs. They include the petals, collectively called the corolla and the sepals, which is the ring of leaf-like structures just under the petals that once comprised the flower bud. The sepals are often called the calyx. Some flowers have no petals but colorful modified leaves, called bracts.
The androecium includes all male sexual organs in a blossom, regardless of numbers. An individual male floral organ is the stamen, with a stem-like filament that holds the anther. The cylindrical anther is often ribbed and splits open to release pollen grains. Depending on species, anther numbers range from a few to hundreds in each flower.
The gynoecium is the all-encompassing term for all female sex organs. Individually, a flower has a pistil, composed of the style, stigma and ovary. The tip of the pistil, where pollen grains are received, is the stigma, which often is sticky. The neck of the pistil is the style and leads to the swollen base of the pistil where the ovary is housed. The ovary may be one mass or made up of several compartments called carpels, in which one or more ovules rest. The ovule, once fertilized, becomes a seed.