What is the function of pistil ?

The pistil's function is reproduction. The stigma, the head of the pistil, provides a place for pollen grains to land and germinate. The style, the long part of the pistil, provides protection for the pollen tube that emerges from the pollen grain and grows down the inside of the pistil into the ovary. The ovary houses the ovule(s) which is fertilized and becomes a zygote(s) when the pollen tube(s) grow through the micropyle of the ovum and releases sperm.