Pollen grains. Coloured scanning electron micrograph (SEM) of bindweed (Calystegia sepium) pollen grains (blue). There is great variation in the size, shape and surface texture of pollen. The often highly-sculpted outer wall (exine) may help in pollen dispersal. Each pollen grain supplies a male gamete (male sex cell) that can fertilise the female gamete in an ovule that will develop into a plant seed. Magnification: x580 at 6x7cm size.