278 THE ICE AGE IN CANADA. 



31. Denticula lauta. Rolling River, Manitoba. 



32. Licmophora (?). Rolling River, Manitoba. 



33. Cocconeis. Rolling River, Manitoba. 



None of th© plants above mentioned are properly 

 arctic in their distribution, and the assemblage may be 

 characterized as a selection from the present Canadian 

 flora of some of the more hardy species having the most 

 northern range. Green's creek is in the central part of 

 Canada, near to the parallel of 46°, and an accidental 

 selection fi'oni its present flora, though it might contain 

 the same species found in the nodules, would certainly 

 include with these, or instead of some of them, more 

 southern forms. More especially the balsam poplar, 

 though that tree occurs plentifully on the Ottawa, would 

 not be so predominant. But such an assemblage of drift 

 plants might be furnished by any American stream flow- 

 ing in the latitude of 50° to 55° north. If a stream flow- 

 ing to the north it might deposit these plants in still 

 more northern latitudes, as the McKenzie river does 

 now. If flowing to the south, it might deposit them to 

 the south of 50°, In the case of the Ottawa, the plants 

 could not have been derived from a more southern 

 locality, nor probably from one very far to the north. 

 We may therefore safely assume that the refrigeration 

 indicated by these plants would place the region bordering 

 the Ottawa in nearly the same position with that of the 

 south coast of Labrador fronting on the Gulf of St. 

 Lawrence, at present. The absence of all the more arctic 

 species occurring in Labrador, should perhaps induce us 

 to infer a somewhat more mild climate than this. 



The climatic indications afforded by these plants are 

 not dissimilar from those furnished by a consideration of 

 the marine fauna of the period of the Leda clay. 



