Sweet pea pollination. Coloured scanning electron micrograph (SEM) of pollen grains (yellow) on the stigma (green) of a sweet pea flower (Lathyrus odoratus). The pollen grains, which contain male genetic material, have become trapped by the stigma's papillae (hair-like structures, green). The stigma is part of the female reproductive structure (pistil), which is formed from one or more carpels. Each carpel consists of a stigma, a style and an ovary (not seen). If the female sex cells (ovules) in the ovary become fertilised by the pollen grains' male sex cells, the carpel may ripen to produce a fruit containing seeds. Magnification: x170 at 6x7cm size.