General Pollen Structure Research

Mature angiosperm pollen grains are specialized cells that contain complete sperm cells. This structure develops after meiosis, when cell division produces two unequally sized cells. The larger of the two cells then absorbs the smaller one. The smaller cell undergoes secondary mitosis to produce two sperm cells required for double fertilization.

Gymnosperm pollen grains are similar to angiosperm pollen grains, but are also very different.
These pollen grains have a unique cell wall. At maturity, these pollen grains have three main components that vary between species.
These components are:
1. A strong, chemically resistant polymer lining.
2. A cellulose inner intine.
3. A Pollen coat, composed of lipids, that contains all subsequent components relating to pollen such as pigment.

http://upload.wikimedia.org/wikipedia/commons/a/a4/Misc_pollen.jpg





Sources:
http://www.plantcell.org/content/16/suppl_1/S84.full