Cedar pollen. Coloured scanning electron micrograph (SEM) of pollen grains from a cedar tree. The characteristic outer wall, or exine, of pollen grains is used by botanists to recognise and classify plants. Each pollen grain contains a male gamete (sex cell) that is intended to fertilise an egg or ovule (female gamete) and initiate the formation of a seed for a new plant. These pollen grains are an allergen that may cause hay fever in susceptible individuals.