The flower is made up of four floral parts. These are:

1. The calyx

2. The Corolla

3. The androecium

4. The gynoecium 

        These floral parts are usually arranged in concentric rings, one above the other, on the receptacle or thalamus. 

        The calyx consists of sepals which are usually small and green. This protects the flower which is in the bud. The outermost whorl of a flower is made up of three to five sepals. They may be separated i.e polysepalous or joined to form a cup i.e gamosepalous. 

         The corolla which is known as the petals form the second whorl or floral part inside the sepals. In many plants, they are the eye-catching part of the flower. Most flowers have four to ten patals which maybe separated i.e polypetalous or joined to form a tube i.e gamopetalous. Generally, petals are brightly coloured and scented which attract pollen-transferring animals. When both the petals and sepals look alike, e.g lilies, they are collectively known as perianth.

          The androecium are the male reproductive organs of a flower. The whorl inside the petals is a group of stamens collectively known as the androecium. Flowers may have three to numerous stamens which may be free or united. In some flowers, the filaments are united while the anthers are free.

           The gynoecium are the female reproductive organs of a flower. It is the innermost whorl of a floral parts of a flower. The gynoecium consists of carpels. It may consist of one, a few or many carpels. A separate carpel or a single structure of several fused carpels is called a pistil.

           A pistil with a single carpel is described as monocarpous e.g flamboyant, while the one with two or more carpels is known as polycarpous, e g hibiscus. When the carpels are free from one another, the pistil is said to be apocarpous, e.g rose flower, but when they are fused together, it is described as syncarpous.

Pistil consistes of the ovary, style and stigma.

Reference

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