The chemical structure of sporopollenin that covers most spores
makes them stable and strong. Therefore, spores are well preserved even in
sediments for those that settle and do
not sprout. Thes spores vary (in size and shapes) by plants hence paleontologists use this uniqueness to determine the types of plants that grew in the past. By comparing those ancient plant
with today's, they are able to extrapolate
the changes in climate that resulted in the extinction
of evolution of particular plants.
