LOCUST, COFFEE-BEAN AND RED-BUD 205 



because of the combination of high mountains and seas along its 

 southern border which effectually barred the ebb and flow of life 

 that took place in Asia and North America with the advance and 

 retreat of the successive ice sheets. During the maximum extent 

 of the ice only a fraction of the Northern Hemisphere was covered 

 and Asia was largely ice-free. The southern hmit of the ice in 

 Europe, where the center of accumulation and dispersal was the 

 Scandinavian region, was the German plain. Here in North 

 America the easternmost or Labradoran center of accumulation 

 and dispersal extended its ice fields only as far south as Staten 

 Island on the Atlantic coast, so that there was plenty of room south 

 of the ice for a vast forest and game preserve for the subsequent 

 repopulation of the more northern region. 



There were at least four periods of glaciation which were 

 separated by long intervals during which the ice disappeared 

 except in the far North, and it is in the deposits formed during 

 these Interglacial periods that we find the fossil remains of the 

 Judas-tree. Both the American and the European Judas-tree 

 were already in existence. The former has been found in North 

 Carolina and in the Don River Valley in Ontario. The latter is 

 rather common throughout France as far north as the site of Paris, 

 and at a number of locaHties in Italy. Both the American and the 

 European Judas-trees frequently depart from the normal orbicular 

 or cordate shape of the leaf, widening them and developing an 

 emarginate apex. This may be an atavistic trait, since several of 

 the ancestral forms appear to have normally had leaves of this 

 )e. 



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