118 TREE ANCESTORS 



throughout Eurasia and North America. They are especially 

 prominent in the lignite beds of this age in Europe, which represent 

 fossil swamp deposits. In North America they are found in 

 California and Colorado, eastern North America being especially 

 deficient in Miocene records of terrestrial life. 



Except for Japan the numerous Pliocene forms of alders are 

 confined to European locaHties where they are generally distributed, 

 being especially numerous in France and Italy. At this time again 

 North American plant records are very scanty, although here again 

 there is no reason to doubt the presence of alders on both coasts, 

 since they are found in both regions in the succeeding Pleistocene 

 deposits. 



Of the 7 or 8 alders which have been identified from the 

 Pleistocene, all that have been accurately determined represent 

 still existing forms, which were, indeed, distinctly foreshadowed 

 during the Pliocene. The European alder, Alnus glutinosa, has 

 been found in the Pleistocene of England, Skye, Germany and 

 Hungary. Another species occurs in northern Italy at this time. 

 The hoary alder, Alnus incana, which is today found in all three 

 of the northern continents, occurs in the Pleistocene of Japan. 

 In North America the red alder, Alnus rubra, occurs in Alaska; the 

 smooth alder, Alnus incana, has been found in Maryland, and a 

 third species has been recorded from interglacial deposits in Ontario. 



