Chickweed flower pistil. Colored scanning electron micrograph (SEM) of a chickweed flower (Stellaria media) pistil. Pistils hold a plant's female reproductive structures. They contain one or more carpels, which, in turn, contain a stigma, style and an ovary. Within the ovaries are the ovules, the female gametes (sex cells). The ovaries are fertilized by pollen grains, the male gametes.