Upon the bog, trees now make their encroachment. Picea 

 nigra is the pioneer. Associated with it, but coming later 

 and less abundantly, are Thuya occidentalis and L,arix 

 Americana. In places this advancing forest zone is strongly 

 Thuya and seems to be associated with the old rocky inlet. The 

 remaining four-fifths of this border zone is dominantly Picea. 

 When this zone closes in upon the bog, as it already has for 

 some distance, the conditions within are constantly made 

 more and more mesophytic and we have a mesophytic under- 

 growth advancing from the surrounding mesophytic Climax 

 forest. Among these mesophytic forms which closely follow 

 the advance of the spruce are Coptis tri folia, Trientalis ameri- 

 cana, Clintonia borealis, Cornus canadensis, Chiogenes serpyl- 

 lifolia, Trillium undulatum, and Osmunda cinnamomea. The 

 characteristic mesophytic shrubs Nemopanthes fascicularis and 

 Amelanchier oligocarpa are also present. 



The entire absence in the bog of orchids such as Calopogon 

 pulchellus, Arethusa bulbosa, Pogonia ophioglossoides, and 

 Habenaria hyperborea, so characteristic of sphagnum bogs of 

 lower altitudes in Maine, seems a peculiar fact of distribution. 

 Isolation has doubtless precluded their appearance. 



The future of this bog is very evident. With the continual 

 advance of the mesophytic forest, the bog will gradually disap- 

 pear and the climax forest will one day blot out its history. 



The strong mountain affinities of this bog flora may be now 

 noticed. The possession, in common with the mountain flora, of 

 the majority of the typical bog forms, especially V actinium 

 uliginosum, V . Vitis-Idaea, and Empetrum nigrum, would seem 

 to strongly indicate an identity of physiological conditions and 

 suggest a common cause. We have already shown that the 

 vegetation of the higher slopes was probably subjected to a high 

 "transpiration ratio" due to a minimized absorption and an 

 accentuated transpiraton. Similarly this high "transpiration 

 ratio" exists in the bog and in the Arctics, and in all these varied 

 habitats there is a striking identity not only specifically but 

 ecologically, thus demonstrating the physiological similarity 

 of these habitats. Such soils are said to be physiologically dry, 

 in other words xerophytic. 



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