The flower is the reproductive organ of angiosperm plants. Flowers that have male and female reproductive organs are called hermaphrodites (or mono).
Flowers that have reproductive organs of only one sex (male or female) are called dioecious.
A hermaphrodite flower is usually made up of four sets of modified leaves, the floral whorls. The whorls fit into a specialized branch called the floral receptacle. The four floral whorls are the Cup, consisting of the sepals, the corolla, consisting of the petals, the androceu, consisting of the stamens, and the gyno, consisting of carpels.
Complete and incomplete flowers
A flower that has the four floral whorls, ie chalice, corolla, androceu and gynoecium, is a complete flower. When one or more of these components are missing, the flower is called incomplete.
Chalice, Corolla and Perianth
The sepals are usually green and resemble leaves. They are the outermost parts of the flower and their function is to cover and protect the flower bud before it opens. The set of sepals forms the floral chalice.
Petals are usually colorful and delicate structures located internally to the sepals. The cluster of petals forms the corolla.
The set formed by the two outermost floral whorls, the chalice and the corolla, is called perianth (from Greek Periaround and anthos, flower).