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Wax plant pollen grains. Coloured scanning electron micrograph of pollen grains of the wax plant, Hoya carnosa. Pollen grain size, shape and surface texture differ from one plant species to another. The outer wall (exine) of the pollen in many plant species is highly sculpted which may assist in wind, water or insect dispersal. These grains are triangular and smooth-walled, indicating wind dispersal. Pores in the pollen wall help in water regulation and germination. Pollen contains the plant's male gametes. These fertilise the eggs or ovules, initiating formation of plant seeds. Pollen also causes hay fever. Magnification: x700 at 6x7cm size. x2340 at10x8ins (KEYSTONE/SCIENCE PHOTO LIBRARY/SCIENCE PHOTO LIBRARY)