Pollen grain. Coloured scanning electron micrograph (SEM) of a pollen grain from a hazel tree (Corylus sp.). Plants release pollen grains to carry male gametes (sex cells) to fertilise the female parts of flowers and produce seeds. The sculpted surface helps this pollen grain to disperse on the wind. Hayfever is an allergy to pollen. In Northern Europe, hazel pollen is one of the most common triggers for hayfever. The tree pollen season is usually spring and early summer. Magnification unknown.