eration has shown us that the interaction of these complex 

 agencies has probably determined the coniferous nature of this 

 forest. 



In contradistinction to these comprehensive and far-reaching 

 climatic factors, are those which are decidedly local in their 

 effects. Mount Ktaadn presents within itself a varied physiog- 

 nomy. The Alpine-Tundra, the heath, the cliff bogs, the 

 Krummholz, and the alpestrine meadow are but phases resulting 

 from the local influence of the several co-operating factors. Yet 

 these many and distinctive plant societies are all within the same 

 climatic formation. Rising as Ktaadn does, from an extensive 

 lowland, it introduces abnormal climatic conditions for this 

 region. Its height brings about new relations as to exposure, 

 light, moisture, wind, and temperature which are superimposed 

 upon the normal climate of the region. We may expect then the 

 physiognomy of these mountain societies to be in direct response 

 to the resultant of the imposed conditions. 



In the section of this paper devoted to the origin of the Ktaadn 

 flora, we recognized and commented upon the strong resem- 

 blance our mountain flora bears to that of regions far to the 

 north, but at that time offered no suggestion as to why this iso- 

 lated Arctic flora had been able to so successfully sustain itself 

 there. We have upon Ktaadn a flora which is probably much 

 like the climax type of Labrador and Arctic North America but 

 which is here, as noted above, largely determined by local climatic 

 conditions: that is we have repeated in a local way upon high 

 mountain peaks the far-reaching climatic conditions of regions 

 farther to the north. Or, in other words, a mountain repeats 

 altitudinally conditions latitudinally true of more Arctic regions. 

 In concluding this general discussion, it may be well again to 

 emphasize the existence of a local climate as well as a general 

 one; the former condition is strikingly exemplified upon high 

 mountains. 



These local climatic factors are several : heat, light, and wind 

 may be mentioned as the most significant. Operating through 

 space they act directly upon the aerial parts of plants through 

 the atmospheric medium which surrounds them. Other parts 

 are affected indirectly, as will be brought out in the following 



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