The flower is a modified shoot of limited growth. The stalk of the flower is called pedicel. At the free end of the pedicel, the flat broad platform forms the thalamus. Four types of modified floral leaves are arranged in four definite whorls on the thalamus. These whorls are Calyx, Corolla, Androecium and Gynoecium. The calyx consists of sepals, corolla of petals, androecium of stamens and gynoecium of carpels.
The calyx and corolla only help in the act of reproduction and do not take part directly in the process hence these are called nonessential or accessory whorls. The androecium is the male whorl whereas gynoecium constitutes the female whorl. These are called essential whorls as they take part in the process of reproduction
