390 . BOTANICAL GAZETTE [may 



stances. In that publication experimental data were given to show- 

 that the toxicity of bog water and of the bog-soil substratum can be 

 corrected by various methods, and that the plants grown in solutions 

 thus treated show not only accelerated growth and an increase in 

 transpiration, but also an increase in the green and dry weight of 

 organic matter. 



It is not known, as yet, whether the toxic action of bog water and 

 bog soil is determined by the action of one constituent or by the com- 

 bined action of several. The experiments so far completed have 

 given no definite evidence that the toxins are merely specific excretions 

 from the roots and rhizomes of bog plants. Preliminary tests, not 

 here detailed, which were carried on in the winter of 1907, indicate 

 that the toxicity may be due to a certain unstable body, of the nature 

 of organic compounds excreted from the roots in the absence of 2 

 and in heavy clay soils not adequately aerated. It is probably a 

 product of imperfect oxidation and decomposition of proteins and 

 other related substances, and it is possible that in respiration bog 

 plants differ from other plants. Since then an excellent account has 

 appeared by Stoklasa (12), in which similar results on the excre- 

 tions by roots are announced. Largely, however, the toxicity of 

 bog water seems to be due to another cause. During the changes 

 which the accumulated plant material undergoes in the process of 

 peat-making, there are alterations and reductions leading to gaseous 

 and colloidal products but little known. The relative amount of 

 these varies with the seasons, and no doubt also with the locality, 

 but primarily it depends upon the stage in the progress of decompo- 

 sition. CH 4 and H 2 S, though produced in small quantities, have 

 been found to constitute the principal gaseous products. They are 

 especially noticeable when well-corked jars of bog water remain 

 standing for some time. Studies on the character of the colloida 

 products are still in progress. The injurious products of a micro- 

 flora accumulating in definite layers of the soil are, perhaps 

 additional factor to be considered. Indeed, it is a serious difficu ty 



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category or broken up into a number of what often prove t 

 arbitrary categories, in order to arrive at results in any way intelbgi e. 



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