Purple echinacea pistils. Macrophotograph of pistils of purple echinacea (Echinacea purpurea) or eastern coneflower. A pistil is the female reproductive structure, composed of one or more carpels. Each carpel possesses a stigma, style and an ovary. Some pollen is also seen (yellow) on the tips of ripe stamen. The fresh roots of this plant are used in herbal medicine. They are can be taken as a tincture to boost the immune system.