Pollination. Coloured scanning electron micrograph (SEM) of part of a flower's pistil with pollen grains attached. The pistil is the female reproductive part of a flower, comprising one or more carpels. Here, many carpels (projections) can be seen with pollen grains (balls) attached to the sticky tips of each carpel, called stigmas. Each carpel comprises a stigma, a style (the projection between stigma and ovary), and an ovary containing eggs (not seen). Pollen, the male sex cells of a flowering plant, lands on the stigma and burrows down through the style to reach the ovary at the style's base. It then fertilises the ovum there, forming a seed.