Hazel pollen grains. Coloured Scanning Electron Micrograph of pollen grains from the Hazel tree Corylus avellana. These microspores are shed from male catkins (hanging pollen-bearing structures) on the Hazel tree, released into the air and carried by wind to pollinate the female flowers. Pollen grain shape, size and surface sculpturing varies greatly between species, and may be used by botanists to identify plants from pollen grains. Large quantities of Hazel pollen occur as a fine yellow mist at springtime in parts of Europe, and may contribute to attacks of hay fever (allergic rhinitis). Magnification: x650 at 6x7cm size.