Hollyhock pollen. Coloured scanning electron micrograph (SEM) of pollen grains of the hollyhock, Althaea rosa. The outer wall (exine) of each pollen grain has a spiky structure; these surface projections may serve to adhere the pollen to insect pollinators. The pollen is tranferred to the stigma of the flower, where it fertilises the ovules in the female ovary to form seeds. Hollyhock is a herbaceous and medicinal plant with white, pink, red or purplish flowers. The pollen may play a role in allergic reactions. Magnification: x202 at 6x6cm size.