Pollen grains carry the sexual cells of plants from one flower to another. According to Pacific Union College, plants produce cells that give rise to pollen in each of four pollen sacs residing on each of the flower's anthers. Each pollen-producing cell divides, producing four discrete pollen grains. The sperm cells found in the pollen fertilize the ova found in female flowers, initiating development of the new plant.
Plants use a variety of strategies to transport pollen grains from one flower to another. According to the United States Forest Service, wind, water and animals are important vectors for this transfer. To attract animals, plants have evolved enticements, traps and attractive odors that draw pollinators to the flowers. Many that rely on animals for pollen dispersal have co-evolved with their primary pollinators, and both depend on each other for survival.
Pollens exhibit great diversity and each species produces its own specific type of pollen. According to a 2004 study published by the American Society of Plant Biologists, female angiosperms, or flowering plants, can detect the differences between pollen from other members of their species. They embrace the familiar pollen of their conspecifics, while they reject those that originated in other species.