Pollen grains. Coloured Scanning Electron Micro- graph of pollen grains of the sunflower, Helianthus annuus. Pollen grain size, shape and surface texture differ from one plant species to another. The outer walls (exine) of these pollen grains are covered with spikes which allow them to catch on the bodies of insects, aiding cross- pollination. The form of the pollen grain wall is also used by botanists to identify plant species. Pores in the pollen wall help in water regulation and germination. Pollen grains contain the plant's male gametes which fertilise the female egg (ovule) to produce a seed. Pollen also causes hay fever. Magnification: x1,125 at 5x7cm size. x3,800 at 10x8"~LANDSCAPE"