ALPINE AND ARCTIC PLANTS 439 



American continent and re-elevated its land have occupied long 

 periods. Whether, with Lyell, we measure these periods by 

 the recession of the Falls of Niagara, or by the growth of the 

 alluvial plain of the Mississippi ; or, with Agassiz, by the exten- 

 sion of the peninsula of Florida, or endeavour to estimate the 

 time required for the abrasion and deposition of the great mass 

 of clay that fills the valley of the St. Lawrence, and allowing 

 for the reductions of the antiquity of the Glacial period arising 

 from recent observations and calculations, we cannot suppose 

 that less than 8,000 or 10,000 years have elapsed since the 

 Alpine plants of the White Mountains were cut off from all 

 connection with their Arctic relatives. Their reign upon the 

 mountain tops not only antedates all human dynasties, but 

 probably reaches beyond the creation of man himself, and many 

 of his contemporaries. 



Positive evidence of the existence of some of these plants 

 during a large portion of this lapse of time has actually been 

 preserved in the Pleistocene deposits of Canada. At Green's 

 Creek, on the Ottawa, in nodules in the clay containing marine 

 shells, and coeval with the Leda clay of Montreal, there are 

 numerous remains of plants that have been embedded in this 

 clay at a time when the Ottawa valley was a bay or estuary, and 

 when the Adirondack Mountains of New York and the moun- 

 tains of New England were two rocky islands, separated from 

 each other and from the mainland on the north by wide arms 

 of the sea. The plants found in these nodules all appearto be 

 of modern species. Several of these plants are found on the 

 White Mountains, and they are all northern or boreal, but 

 scarcely Arctic, belonging as they do to the southern margin of 

 the Arctic land species. I have no doubt that further examina- 

 tion of these deposits will lead to the discovery of additional 

 examples. This fact, proving as it does the existence of these 

 species at the period in which the theory of Lyell and Forbes 

 requires them to have migrated, is in itself strong corroborative 



