Describe essential organs of a flower.

Essential whorls of a flower include Androecium and Gynoecium

Androecium: It consists of individual members called the stamens. Each stamen is differentiated into a stalk called the filament and a microspore (pollen grain) producing structure the anthers also known as microsporangia. The anthers may be monothecous or dithecous. The anthers produce pollen grains or male gametophytes and are attached to the filament.

Gynoecium: It is the innermost whorl of the flower, individual members are called pistil or carpel. Each pistil is differentiated into stigma, style and ovary.

The stigma has distinct shapes to hold and anchor the pollen grains like feathery in Poaceae, Bifid,pentafid etc 

The style is a hollow structure that helps in the movement of pollen tube towards the ovary.

The ovary has ovules or the megasporangia attached on its inner wall, that produces the female gametophyte or the embryo sac that contains the female gamete or the egg.