1919I RIGG &- THOMPSON— BOG WATER 369 



with two samples from the North Mud Lake bog and one sample 

 from each of the following bogs: Maltby bog, Henry bog, and the 

 bogs at Cordova, Alaska, and Sand Point, Alaska. The results 

 in all cases were the same. The work was then repeated by 

 saturating samples from these same bogs with NaCl, MgSO^, and 

 Na,HP04. The results in all cases were the same qualitatively as 

 when (NH4),S0^ was used, although the quantity of precipitate 

 varied somewhat. Later precipitation of samples from these bogs 

 and other bogs of the Puget Sound region was tried repeatedly, 

 and in all cases the results were as described. 



The precipitate from 7 samples treated with (NH4)2S04 was 

 filtered off on filter paper. Each filtrate was then placed in a 

 dialyzing tube of parchment paper and dialyzed in running water 

 until the contents of the tubes showed no precipitate with barium 

 chloride. The toxicity of these filtrates was then tested by grow- 

 ing cuttings of Tradescantia in them in the same way that the 

 toxicity of bog water had been tested earlier (10). Controls of 

 Tradescantia cuttings in untreated bog water and in Cedar River 

 water were run. The root hairs developed well in the filtrate and 

 in the Cedar River water, while their development was very poor 

 in the bog water. No difference could be seen between those 

 grown in the filtrate and those in the Cedar River water. Samples 

 of bog water were also dialyzed and cuttings of Tradescantia were 

 grown in them. They were still just as toxic as untreated samples. 



On January 25, iqi8, 6 samples of bog water that had been col- 

 lected from Henry bog on November 5, 1916, and filtered through 

 filter paper on November 7 and again on November 9, 1916, were 

 all found to contain considerable quantities of a brown precipitate 

 in irregular, somewhat flaky, masses. A sample collected from 

 Maltby bog on November 30, 1915, and, filtered December 4, 

 191 5, showed the same results, as did also one collected at Sand 

 Point, Alaska in July 19 13, and filtered October 27, 191 5. A 

 gradual aggregation of the colloidal material occurred with the 

 lapse of time in every case. 



In order to test the volatility of the toxic substances, 500 cc. 

 of the filtered bog water was distilled on a water bath until the 

 residue was only 80 cc. The distillate was colorless, while the 



