In geological age, while the Franz Josef flora resembles most the previously known Jurassic floras of Siberia and Spitzbergen, yet Nathorst considers the geological age different, and naturally places it between the two, it being evidently younger than that of Siberia. It is interesting to note that Doctor Koettlitz found in an isolated basalt nunatak (rock or hill protruding from a glacier) fossil plants similar to those found by himself and Nansen on the north side of Cape Flora. These nunatak plants, which Koettlitz believed to be _in situ_, are identified by Nathorst as Upper Jurassic, and came from an elevation variously estimated as from six hundred to seven hundred and fifty feet above the sea. Nansen agrees with Koettlitz in believing that tree-trunks found by them, charred into charcoal or partly silicified, chiefly belonged to conifers growing on the soil over which basalt flows were discharged during the Upper Jurassic or Lower Cretaceous age, and that they have been charred by a flowing mass of lava that overwhelmed them. These fossil plants tell the story of tremendous physical changes which have produced very important modifications in climatic conditions in the Arctic regions. The changes in the types of vegetable life are apparently as extensive in high as in low latitudes. The lower cretaceous flora is almost tropical, as is shown by the predominating forms of this vegetation. Carboniferous formations obtain extensively in the Arctic regions, as they occur in the Parry Archipelago, Spitzbergen and in Siberia. During the carboniferous age there was a great extent of land near the North Pole closely resembling that of the temperate latitude of the same period, as is shown by the small number of fossil plants that are peculiar to the Arctic regions. In the tertiary period miocene flora flourished in Spitzbergen, where even the lime, the juniper and poplars have been found near latitude 79 N. Then also throve sequoias, which closely resemble trees growing in the southern part of the United States. The miocene flora gives evidence of a very great contrast between the climatic conditions at that epoch between Europe and the Arctic regions. The cretaceous flora throws important light on the changes of climate in the Arctic regions, and, as has been pointed out, the tropical forms predominate in the vegetation of the Lower Cretaceous flora. Heer’s prediction that the plants found on the west coast of Spitzbergen would also be found on the East Greenland coast has been fully verified. Miocene plants have been found from Spitzbergen westward through Iceland and Greenland to Banks Land and in the Parry Archipelago, and it is interesting to note that more than one fourth of the Arctic plants are common to the miocene of Europe; in Greenland and on McKenzie the percentage is nearly one half.