Cenozoic. Quaternary. Recent. Pleistocene (glacial). *Tertiary. Pliocene. *Miocene. Oligocene. Eocene. Mesozoic. Cretaceous. Jurassic. Triassic. Paleozoic. Carboniferous. Devonian. Silurian. Ordovician. Proterozoic. Cambrian. Algonkian. Archean. CLIMATE DURING THE LIFE OF THE FOSSIL TREES. A final word may be added regarding the probable climate of the region during the lifetime of these fossil forests. It is obvious that the present flora of the Yellowstone National Park has comparatively little relation to the Tertiary flora and can not be considered the descendant of it. It is also clear that the climatic conditions must have greatly changed since Tertiary time. The Tertiary flora appears to have come from the south, but the present flora is evidently of more northern origin. The climate during Tertiary time, as indicated by the vegetation, was temperate or warm-temperate, not unlike that of Virginia or the Carolinas at the present time, and the presence of numerous species of figs, a supposed bread-fruit tree, cinnamons, bays, and other southern plants indicates that it may have been almost subtropical. However, the conditions that were favorable to this seemingly subtropical growth may have been different from the conditions now necessary for the growth of similar vegetation. It may be that these supposed subtropical plants were at that time so constituted as to grow in a temperate land, and that they may have become tropical in recent times. Following this general line of thought it may be said that although the Tertiary vegetation of the Yellowstone National Park would now be regarded as indicating a temperate or even warmer climate, the actual climate may not have been subtropical. It is certain, however, that the conditions were very different from those now prevailing in the park. PUBLICATIONS ON YELLOWSTONE NATIONAL PARK. DISTRIBUTED FREE BY THE NATIONAL PARK SERVICE. The following publication may be obtained free on written application to the Director of the National Park Service: Circular of General Information, Yellowstone National Park (issued yearly). This pamphlet contains general information of interest to the tourist. SOLD BY THE SUPERINTENDENT OF DOCUMENTS.[3] The following publications may be obtained from the Superintendent of Documents, Government Printing Office, Washington, D. C., at the prices given. Remittances should be made by money order or in cash: