Simple diagram displaying morphology of a pollen grain
Structure of the pollen grain

The pollen grain is made up of three main concentric layers. The central part is the living cell, the cytoplasmic interior, which germinates on the stigma. The intermediate layer is called the intine and envelops the whole of the grain in a uniform sheath. The intine has a debatable composition due to the relative lack of research on it, but consists, to some degree, of cellulose. The outer layer is called the exine. This is the part of the pollen grain that is composed of sporopollenin, one of the most amazingly resistant organic materials. The latter is arranged in complex forms in the pollen wall. This wall does not perish and its high resistivity to damage and decay makes it likely to get preserved in the fossil record, as opposed to the other two components. For this reason, more information is known about the exine. Pollen walls, apparently unchanged, are found in Paleozoic (and even older) rocks in which other organismsí remains have been distorted and carbonized.

The Wall