sporopollenin

…outer coat, or exine, contains sporopollenin, a chemical that is extremely resistant to decay). Leaves, wood, and well-preserved flowers also have been recovered from Early Cretaceous sediments. At one time, angiosperms were thought to have appeared suddenly (“explosively”) and with such diversity in structure that it was theorized that they…

…the exine have been termed sporopollenins. The internal parts of the pollen grain are easily broken down, whereas the exine layer, and thus the general form of the pollen grain, is easily preserved in various kinds of sediments; the quality of preservation may vary with different environments.

…a highly decay-resistant chemical called sporopollenin. The exine usually has one or more thin areas, or pores, through which the pollen tubes germinate, and the thick area of the exine is usually highly sculptured. The number of pores and pattern of exine sculpturing are characteristic within an angiosperm family, genus,…