Pollen grains, computer artwork. Pollen grains are reproductive structures produced by flowers. They display a great variation in their size, shape and surface texture. The outer wall (exine) is often highly sculpted to aid in their dispersal on the wind and by pollinators such as insects. Flowers may collectively produce many hundreds of millions of pollen grains in a flowering season. The pollen grain surfaces are used by botanists to categorize and recognize plants. Each pollen grain contains a male gamete (reproductive cell) that is intended to fertilise an egg or ovule (female gamete), and initiate the formation of a seed for a new plant.