Pollen. Coloured scanning electron micrograph (SEM) of pollen grains of the hollyhock (Alcea rosea) and the sunflower (Helianthus sp. ). The hollyhock pollen grains (large, orange) are very large, and the sunflower grain (pink) represents a more average size for flower pollen. The outer wall (exine) of each pollen grain has a spiky structure, and these surface projections may serve to adhere the pollen to insect pollinators. The pollen carries the male genetic information of the plant. It is transferred to the stigma of a flower, where it fertilises the ovules in the female ovary to form seeds. Magnification: x250 at 6x4.5cm size.