176 TREE ANCESTORS 



of North America and the Arctic archipelago to the northward had 

 been a land area for many millions of years pre\dous to their mar- 

 ginal flooding by the Upper Cretaceous sea. This fact is more 

 significant than it may seem at first sight. The latest marine 

 submergence of the Appalachian province, using that term in a 

 very broad way had been the dwindling sea of the Carboniferous. 

 This area and that lying north of it to the pole itself was a land 

 area during all of Permian, Triassic, Jurassic and Lower Cretaceous 

 times. When this land first emerged from the Carboniferous sea 

 it was clothed with a strange vegetation made up of entirely extinct 

 types, such as the seed-ferns, Calamites, lepidodendrons and sigil- 

 larias. During the interval between the Carboniferous and the 

 Upper Cretaceous the foregoing types had become entirely extinct 

 and the flowering plants had been evolved and had rapidly spread 

 toward that dominance in the plant world which they occupy at 

 the present time, which position they had reached as eariy as 

 Eocene time. This holds a still greater interest for the human race, 

 since practically all plant foods utihzed by man, and the plant 

 foods utihzed by the animals upon which man depends for meat 

 (except fishes) are derived from the flowering plants, and it is no 

 exaggeration to say that fixed abodes and agriculture which were 

 the basis of civiHzation itself were conditioned upon the evolution 



Fig. 38. Fossil Leaves or the Tulip-tree (About § Natur.\l Size) 



L Liriodcndron meeki Heer from the Upper Cretaceous of Alabama. 



2. Liriodendron quercijolium Newberry from the Upper Cretaceous of New 

 Jersey (Raritan formation). 



3. Liriodcndron viorganensis Berry from the Upper Cretaceous of New Jersey 

 (Magothy formation). 



4. Liriodendron alatum Newberry from the Upper Cretaceous of Colorado 

 (Vermejo formation). 



5. Liriodendron acuminatum Lesquereux from the Dakota sandstone of 

 Kansas. 



6. Liriodendron procaccinii Unger from the Tliocene of France. 



7. The same from the Phocene of Italy. 



8. Liriodendron islandicum Saporta & Marion from the Eocene of Iceland. 



9. Liriodendron gardncri Saporta from the Eocene of England. 



10. Liriodcndron tulipifcra Linnaeus from the Pleistocene of North Carolina. 



