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ANNUAL REPORT SMITHSONIAN INSTITUTION, 1918. 



Asia to China and Japan. Fossil forms are found as early as the 

 Upper Cretaceous, at which time at least a dozen species, all North 

 American, have been described, seemingly indicating an American 

 origin for the genus. The leaves are not common in the lower Eocene 

 but the characteristic peltate fruits are not rare, and the two com- 

 bined have furnished the data for the restoration shown in figure 42. 

 Comparable floras are found in Europe in the Paris basin, along 

 the south coast of England, and elsewhere. 



With the passing of events the climate gradually became warmer, 

 as attested not only by the terrestrial floras on both sides of the At- 

 lantic, but by the 

 contemporaneous ma- 

 rine faunas, until, 

 during the upper 

 Eocene and lower 

 Oligocene, the cli- 

 mate of our Gulf 

 tier of States and 

 southern Europe be- 

 came strictly tropical 

 and was overrun by 

 an appropriate 

 tropical vegetation, 

 while the temperate 

 forest pushed into 

 the polar regions un- 

 til most, if not all of 

 the lands within the 

 Arctic Circle and 

 part at least of the 

 Antarctic continent, 

 were forested by cool 

 temperate types. 



The most extensive 

 of these polar floras 

 is that recorded from western Greenland (latitude 73°), which in- 

 cluded nearly 300 different species. Eighteen of these are ferns; 28 

 are conifers, including the Ginkgo, incense cedar, cypress, and nu- 

 merous sequoias and pines; 21 are monocotys, including two palms; 

 and a vast abundance of diocotyledonous leaves of willow, poplar, 

 alder, hazel, beech, oak, elm, sycamore, walnut, ash, service berry, 

 sumach, dogwood, gum, grape, magnolia, maple, holly, buckthorn, 

 hawthorn, etc. 



Traces of this flora are found in Grinnell Land, Spitsbergen, Ice- 

 land, Siberia, and elsewhere to within 8 or 10° of the North Pole, in 

 a region that has since become a desert of snow and ice. In the 



Fig. 42. — Restoration of Paliurus based upon fruits and leaves from 

 the lower Eocene of Mississippi and Tennessee (after Berry), X 1/2. 



