The essential parts of a flower are the androecium and gynoecium. The androecium is the male reproductive part of the flower, which includes the anther and filament. The anther is the part of the flower that produces pollen, and the filament supports the anther. The gynoecium is the female reproductive part of the flower, which includes the stigma and style. The stigma is the part of the flower where pollen lands, and the style connects the stigma to the ovary. The ovary contains the ovules, which develop into seeds after fertilization. While petals and sepals may play important roles in attracting pollinators and protecting the flower, they are not considered essential for the reproduction of the plant.