440 ALPINE AND ARCTIC PLANTS 



evidence. We can say that some of these species were waiting 

 on the shores of the north, ready to be drifted to the insular 

 spots to the south-west, and that their seeds were actually being 

 washed out to sea by the streams which emptied themselves 

 into the then estuary of the Ottawa. 



Another aspect of the inquiry is that which relates to the 

 reduction of temperature, which might be consequent on the 

 great depression of the land which we know to have existed 

 at the close of the Tertiary period, a fact on which I have 

 insisted in former papers on the Pleistocene deposits of 

 Canada.^ A very clever writer on the subject of geographical 

 distribution^ has pictured the case of a subsiding continent, 

 with the fauna and flora of its lowlands becoming gradually 

 concentrated on the spots which had previously been Alpine 

 summits, but now reduced to. low and temperate islands. But 

 he has left out of view the fact, that if land still existed in mass 

 in the Arctic regions, and if the subsidence was that of land in 

 temperate regions, and if the remaining islands were encom- 

 passed with cold and ice-laden currents, then, on the principles 

 long ago so well stated by Sir C. Lyell, these islands might 

 have a mean temperature far below that of the former plains, 

 and might, in consequence, be suitable only to such an Alpine 

 flora as that which they had previously borne. 



Now this is precisely what seems to have occurred in the 

 Pleistocene period. The Arctic land remained in great mass, 

 detaching into the sea annual crops of icebergs and fields of 

 coast ice, which have strewed all the northern hemisphere with 

 boulders : the temperate regions were submerged, except a few 

 insular spots. These are the very conditions required for a 

 low mean temperature, both in the sea and on the land, and 

 these geographical conditions correspond precisely with the 

 facts as indicated by the fossil animals and plants of the 



* Canadian Naturalisi, vol. iv. ^ Wollaston. 



