The Stamens (collectively called androecium) are the male sexual organ of the flower. A stamen consists of an anther which contains the pollen grains, supported by a filament. When the pollen grains becomes mature in the anther , it is released through the ruptured anther wall.Pistils, which are often called carpels, (collectively called gynoecium) are the female sexual organ of the flower which are usually vase-like in appearance. A pistil may be simple or compound.A simple pistil has a single reproductive unit called a carpel, ; a compound pistil has two or more carpels, often fused, as in grape. A carpel usually consists of three flower parts: the stigma, style and ovary.The stigma is an enlarged tip of the carpel which serves as a “landing pad” to receive the pollen in the process of pollination. This part of the flower is supported by the style which is connected to an enlarged base (the ovary) which contains the ovule. The ovule is borne on a surface called placenta.After pollination and double fertilization, the ovary develops into a fruit and the ovule into a seed.
so in short the essential parts of flower are anther, ovary ,petals