Pollen that is distributed by the wind has to travel large distances. Pollen grains are rather small and their surface is smooth. Only rarely as in the case of Pinus and Picea , for example are they equipped with lateral airsacs. The pollen grains have to stick to each other and to the bodies of the insects. Typical angiosperm pollen is the only proof that this plant group has already existed during the lower Cretaceous and perhaps even in the Jurassic period.
Pollen analyses are also well-suited for the elucidation of the late past of floral history.
Successions of plants representative of bog formation, for example, can be captured that way. The shape of angiosperm pollen is more variable than that of gymnosperm pollen. The exine is subdivided into nexine and sexine. Their tip regions may be partially or completely connected so that they may form a tectum . The space between the columellae is often filled with oily or protein-rich pollen cement.