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Grass pollen dispersal by the wind. This grass is cocksfoot grass (Dactylis glomerata). The pollen grains (upper left) have been shaken loose from the plant by the wind, and will be carried away by the wind to pollinate other D. glomerata plants. The pollen grains contain the male gametes (sex cells). During the flowering season, billions of grains of pollen are spread on the wind, which causes hayfever symptoms in those who are allergic to pollen grains and other wind-borne allergens. (KEYSTONE/SCIENCE PHOTO LIBRARY/EYE OF SCIENCE)