Dr. Cushman envisions Fossil Lake with forests of maple, hickory, oak, chestnut, walnut, alder, and birch found along the shore, with palms growing in the more moist areas and willows flourishing along the streams. Pine, spruce, and fir thrived in the highland areas towering above the lake. Dr. Cushman follows a detailed method of preparation in readying his field samples for laboratory study. Samples of fine-grained mudstone or shale are collected and brought back to the laboratory. Using mortar and pestle, the samples are crushed into smaller fragments.
Hydrochloric acid is added to dissolve the calcite.
Hydrofluoric acid is then added to dissolve the silica. At this point, an organic residue of plant material and algae remains. The samples are mounted on biological slides for study under the microscope. The distinct characteristics of particular pollen and spores make it possible to identify the plants of origin. Dr. Cushman is quick to point out that his research is a small part of a much larger picture.