242 TREE ANCESTORS 



Eocene of Sachalin Island on the east coast of Asia. In North 

 America the Eocene records are numerous, and most abundant in 

 the rocks of late Eocene age, and in our more northern States and 

 still farther northward. 



The southernmost record is New Mexico, the others include 

 Colorado, Wyoming, Montana, California, Oregon and British 

 Columbia. Eocene dogwoods are found in Greenland and Spitz- 

 bergen. One described from Wyoming is based upon a characteris- 

 tic fossilized flower head with the enlarged bracts much like our 

 existing flowering dog\vood. 



The Oligocene records of the dogwood drop to 3 species described 

 from Italy, Prussia and Bohemia. This scanty record for those 

 times is due partly to adverse conditions and partly to the carcitys 

 of plant records of that age, particularly in North America. The 

 record becomes more representative in the succeeding Miocene 

 times for some 20 species of dogwood have been described from 

 deposits of that age. These are mostly European and Miocene 

 species which were widely scattered over Europe at that time from 

 France to Austria and Hungary. In this country 1 form has been 

 found in deposits supposed to be of Miocene age in the Yellowstone 

 Park, and 2 others have been recorded from California. 



In succeeding Pliocene times which brought the Tertiary period 

 to a close the variety and abundance of dogwoods appears to have 

 waned. I say appear, since the Pliocene records are so incomplete 

 that the merely negative evidence may be of no value. Four 

 different dogwoods are reported from PHocene deposits and all of 

 these are from Old World locaHties. This does not mean that the 

 dogwood became extinct in North America during the PHocene and 

 reappeared in modern times — the mere fact that they could not 

 have attained their present day distribution under existing climatic 

 conditions is sufficient proof that this was not the case, but that 

 our American PHocene plant record is very incomplete. 



The Old World PHocene forms have been found in France, Spain 

 and Italy in Europe, and in Japan. The dogwood was thus a 

 member of the forest flora that at that time extended almost un- 

 brokcnly from Portugal eastward to Japan. Traces of this forest 



