Flower Structure and Function
Flowers, the reproductive shoots of angiosperm sporophytes, are typically composed of four types of floral organs: carpels, stamens, petals, and sepals. When viewed from above, these organs take the form of concentric whorls. Carpels form the first (innermost) whorl, stamens the second, petals the third, and sepals the fourth (outermost) whorl. All are attached to a part of the stem called the receptacle. Un-like vegetative shoots, flowers are determinate shoots; they cease growing after the flower and fruit are formed.