by 
The Curious Bag
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Pollen grains are tiny, but each one contains the genetic code necessary to create new life. Pollen is produced by the anthers on the tips of the stamens, the male sex organs of a flower. Here, the grains sit, waiting for a visiting insect or bird to transport them to another flower to complete pollination.
The Exine
Pollen grains are covered by the exine, the outermost layer of the sporoderm or pollen wall. This is a protective covering that contains polysaccharides, which are a form of carbohydrates. It is this acid-resistant shell that makes it possible for pollen to be found in a fossilized state.
The Intine
The inner layer of the sporoderm is the intine. It is made of cellulose and is constructed much like a plant cell. It provides further protection for the reproductive cells.
Male Gametophyte Cells
Each pollen grain has two or three male gametophyte cells. These cells are haploid, meaning they contain half of the chromosomes of the parent plant.
Tube Cell
The tube cell is what develops into the pollen tube once the flower has been pollinated. This tube travels down the style (part of the female sex organ) into the ovary to fertilize the ovules.
The Germ Cell
The germ cell divides into two sperm cells by a process called mitosis. This is where the cell's nucleus divides and the DNA is replicated. This cell division can happen before or after the pollen grain has pollinated a flower.
Source:
EnchantedLearning.com: Flower Anatomy
Emc.Maricopa.edu: Flowering Plant Reproduction: Flower Structure
Geology.iupui.edu: Composition and Structure of Pollen and Spores
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