74 



TREE ANCESTORS 



There is also a walnut on the opposite shores of the Pacific in 

 Manchuria {Juglans mandchurica) and a second in Japan (Juglans 

 sieboldiaiia) . 



The genus is apparently one of the earliest of our still existing 

 trees to appear in the fossil record, leaves suggesting it having been 

 found in the Middle Cretaceous. It is well represented in fossil 

 floras from the base of the Upper Cretaceous to the present, the 

 former horizon furnishing several different forms, one of which 

 named Juglans arctica ranges from western Greenland to Alabama 



Fig. 13. Map Showing Present Range of the Walnuts (solid black) 



AND the Area Over WracH They Are Known to Have Spread 



During Their Past History (lined) 



along the Atlantic coast, and furnishes a striking illustration of 

 the difference between Cretaceous and present day climates. 



There are about 25 species of walnut recorded for Eocene times 

 and at that time they are well distributed over the whole Northern 

 Hemisphere. They are found from the Mexican Gulf region to 

 Alaska and Greenland in North America; and from Sachalin 

 Island off the east coast of Asia to western Europe. 



