MESOZOIC AND TERTIARY FLORAS 209 



The unconformity of the base of these beds together with the differ- 

 ences in the flora, clearly and logically marks the point at which the 

 line is to be drawn between Cretaceous and Tertiary. 



In the Mississippian region in Louisiana and Mississippi we have 

 a small Eocene flora (Eolignitic) comprising palms, evergreen oaks, 

 magnolias, laurels, cinnamomums, etc., which appear to be most 

 closely affiliated with small floras in northern New Mexico and adja- 

 cent Colorado, the latter in turn being most closely related to much 

 larger post-Laramie floras in the Denver Basin of Colorado. These 

 embrace the Arapahoe with about thirty species, and the Denver with 

 nearly two hundred species, and are believed to be slightly older than 

 the Fort Union — in any event, there are only about thirty species 

 in common. 



The Green River formation of upper Eocene age occupies a quite 

 extensive area in central and western Wyoming, and has afforded a 

 flora of some eighty species. It is very distinct from the Fort Union 

 and other Lower Eocene floras, and shows a distinct increase of 

 modern forms. 



In the northern Pacific coast region there are a number of Eocene 

 floras, among them that of the Swauk which occurs just east of the 

 Cascade Mountains in Washington. This large flora is entirely 

 different from any other in this country, and consists of types that are 

 for the most part found in Central and northern South America, 

 among them being palms 6 feet in diameter and in layers sometimes 

 a foot in thickness. This shows that the palms were not sporadic 

 or occasional, and indicates, as do many of the other things, that the 

 climate was mild, probably subtropical. The overlying Roslin for- 

 mation contains a flora that is almost entirely different from that of the 

 Swauk, and lacking the presence of palms was probably slightly 

 cooler than the underlying formation. 



To the northward and covering a vast area in Alaska and well out 

 on the Alaskan peninsula is the Upper Eocene Kenai formation which 

 has afforded a rich flora of oaks, poplars, willows, hazels, walnuts, 

 magnolias, horse-chestnuts, and maples, together with pines, spruces, 

 cedars, and sequoias. This flora is found in British Columbia, and 

 abundantly in Greenland, Iceland, and Spitzbergen, showing that it 

 was of wide extent in similar northern latitudes. It is distinctly a 



