Pollen. Coloured scanning electron micrograph of pollen grains of the chickweed flower Stellaria media (a self pollinating plant). Pollen is dispersed either by insect or wind. Once on the stigma of the plant the pollen grain swells, pushing out the concave surfaces seen here and grows a pollen tube. This grows down the style and into the ovaries at the base of the capsule, where it releases the sperm (gametes) for fertilization with the eggs (ova). The result is the production of seeds. Pollen is an human allergen implicated in attacks of both asthma and hayfever. Magnification:X 460 at 35mm size. Original is bw print b786/175