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1909] D AC H NOW SKI— BOG TOXINS 39I 



conditions; and the more detailed responses which are due to localized 

 influences are thus neglected. On the other hand, even though we 

 decide experimentally which of the physical and chemical variables 

 involved is of greater influence at a given stage, it still remains to 

 determine how the ensemble of factors acts in the process which accom- 

 panies each physiographic change and serves as the functioning basis 

 for morphological differences. 



In connection with the experiments on the presence of injurious 

 substances in bog water and bog soils, and their effect upon agri- 

 cultural plants, the question arose whether the toxins which are 

 harmful to plants in water cultures are injurious also to plants grow- 

 ing in soil containing them. This question has an added interest 

 just now, because facts like those cited above give indications that 



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the sterility of unproductive and "exhausted" agricultural soils may 

 partly be caused by some toxic substance of a similar physiological 

 and chemical origin. Different workers have observed that the growth 

 of plants often gives rise to unfavorable conditions. The data 

 obtained from various lines of experiments all go to prove that 

 exhaustion" cannot always be attributed to the removal of plant- 

 nutrients from the soil by previous crops or by previous plant societies 

 (10). To attempt a review of the literature on this problem would 

 be out of place in the present paper. Suffice it to say that the results 

 thus far obtained point strongly to the view that decreased physiologi- 

 cal activity of plants lies rather in the toxic condition of the soil, 

 r he experimental proof is still regarded by many as furnishing nega- 

 tive evidence upon the problem (6, 9), and hence a spirit of contro- 



of the writings upon this subject. However, 

 !t can no longer be questioned that the solution of this inquiry is of 

 great importance to agriculture. It promises to throw new light upon 

 m any interrelations of soil and plants, and appears to afford a satis- 

 factory explanation of some of the problems connected with the 

 association and succession of plants, which on every other criterion 

 w °uld largely remain an enigma. 



For the purpose of determining whether the toxins of bog water 

 are harmful also to plants growing in soils containing the injurious 

 su bstances, it was decided to employ first of all a soil medium as 

 ne arly non-nutrient as possible. Quartz is one of the chief and most 



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