Pollen

Pollen is known as a powder with pollen grains. These pollen grains make sperm cells that come from seed plants. The grains have a firm coat that protects these sperm cells when they move between the pistil of one flower and another. All pollen grains have a certain vegetative cells that contain nucleuses that can produce new pollen tubes. These pollen tubes are surrounded by a wall called a cellulose cell and a thick outer sporopollenin wall. Pollen particles and grains can come in all sizes, shapes, and species. As a flower develops, groups of sporogenous cells start to form in the pollen sac. Tree pollen is a popular type of pollen that causes many allergies for people.