The exact cause of the low absorption in the sphagnum bog 

 is yet problematical. Two theories are in vogue. Schimper 

 claims 1 that the lack of drainage and aeration causes the 



1. Op. cit. 



abundant accumulations of humus and humic acids. These act 

 upon the roots inhibiting absorptive power. Similarly these 

 ' acids preclude nitrifying bacteria, thus making the soil poor in 

 nitrogen. In all the absorption is reduced to a minimum. 



The other theory, advanced by Kihlman 1 and applied to the 

 sphagnum bog by Ganong, 2 would refer the cause of low absorp- 



1. Opp. cit. 



2. Ganong, W. F. Upon raised peat bogs in the province of New Brunswick. 

 Trans. Roy. Soc. Canada 3: II, 131-163. 3897. 



tion to the low temperature, making this strong ecological and 

 specific resemblance of Arctics, mountains, and sphagnum bogs 

 due to an identical factor. A set of readings by the writer sub- 

 stantiate the latter theory. We have also shown in some pre- 

 liminary experiments that the low temperature of the bog is 

 sufficient to reduce the absorption to a minimum. 



The striking Arctic and Alpine affinity of the sphagnum bog 

 and the border flora of mountain ponds, as noted above, leads to a 

 very significant consideration, the question of their origin. It 

 has been shown above that the Alpine flora is glacial in origin. 

 In view of this fact and the floral similarity between the above 

 plant associations and the Arctics, we are led to suggest a similar 

 explanation. Whether these ponds have received their border 

 floras through local and valley glaciation and avalanche action 

 or by general glaciation, is of course entirely problematical. The 

 former mode would, however, seem more probable and must, 

 at least, have been a source of subsequent introduction of the 

 Arctic- Alpine forms. 



This hypothesis may be extended to extra montane ponds ; in 

 these, however, general glaciation must have been the source of 

 this relict flora. Such a condition as described for Sandy 

 Stream pond might well be taken as an example of the initial 

 stages of such a plant society. The centripetal encroachment of 

 this border zone would eventually develop a typical sphagnum 

 bog, not unlike the one described above and quite identical with 



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