CANADIAN FORESTRY ASSOCIATION 115 



and which we all hope to arrive at, if the objects of this Association are properly 

 carried out. 



I will now call upon Dr. Robert Bell, Assistant Director of the Geological 

 Survey of Canada, to read his paper. 



THE NORTHERN ADVANCE OF OUR FOREST TREES. 



In presenting his paper Dr. Bell first called attention to the very large number 

 of species of forest trees which are native to North America, as compared with those 

 found in the old world, the number amounting to more than three hundred or nearly 

 ten times as many as are indigenous to Europe. In order to account for this great 

 forest wealth it was necessary to go back to a very ancient time, although geologi- 

 cally speaking part of the history was not very remote. 



Until a comparatively recent period in the history of our planet the climate 

 of the earth depended mainly on the heat of the earth itself. The polar regions 

 were the first to become cool enough to admit of plant life at all. For a considerable 

 time tropical vegetation, including forests, flourished in the north polar regions. 

 This was greatly favored by the six months of continuous daylight, while the alter- 

 nating six months of darkness took the place of winter and allowed all plant life 

 to rest. Abundant remains of this northern vegetation are preserved in a fossil 

 state in various parts of the polar regions. These showed that as the earth 

 cooled the polar forests gradually changed to a semi-tropical and then to a tem- 

 perate character. And with the on-coming of the glacial epoch they disappeared 

 altogether, having been driven far southward. 



When the great ice sheets disappeared, and the climate improved in the 

 temperate and north temperate latitudes, many kinds of trees returned northward 

 and re-occupied much of the lost ground. Those species whose seeds are provided 

 with the best means of being carried in the currents of the air overspread the 

 country most rapidly, while others, such as the nut-bearing trees and some other 

 species, could only advance very slowly. It has been found by actual experiments 

 that such species on being artificially transplanted northwards, would flourish and 

 bear fruit far beyond their present natural limits. These and other facts show that 

 some of our native trees have not yet reached their most northern possible limits, 

 while others, such as the populars, birches, willows and conifers have done so. 



The capacity to live further north is shown not only by such trees as the black 

 walnut, hickory, oak, honey locust, etc., but also by species which have attained 

 more northern latitudes by their own efforts, such as the black ash, the ash-leafed 

 maple, and others. 



The fact that the northern limits of some species which are poorly provided 

 with means for advancing, terminates suddenly, without showing gradual diminu- 

 tion in the size of the trees, is an indication that such species are still moving north- 

 ward. All these circumstances show that there has been and still exists a tendency 

 for some of our forest trees to move northward, since the general amelioration of the 

 climate at the close of the glacial epoch. 



I have been studying the exact limits of each species of our forest trees during 

 my extensive travels and explorations for more than forty years past, and have 

 published at various times the conclusions which have been forced upon me. 



The northern limits which I have found do not follow the lines of latitude even 

 approximately, but show many curious eccentricities which can be accounted for 



