376 BOTANICAL GAZETTE [November 



lack of drainage, the place to look for the origin of the toxicity is 

 in the decay of sphagnum under anaerobic conditions. It seems 

 probable (but is not proved) that the acidity, the colloidality, 

 and toxicity all have their origin here. 



It seems clear that the substances in bog water that are pre- 

 cipitated by electrolytes and on long standing without electrolytes, 

 and will not dialyze through parchment paper, and, although 

 present in considerable quantities, do not appreciably lower the 

 freezing point of the water, are in a colloidal state. Since bog 

 water and preparations from it (for example, the concentrate and 

 the solution of the residue from evaporation) which contain these 

 substances are toxic to Tradescantia cuttings, while preparations 

 that do not contain them (the distillate) are not toxic, it appears 

 that the toxicity is associated with the matter that is in a colloidal 

 state. Concerning the nature of the colloid we have the following 

 indications. 



1. The colloid is thermo-stable. This is indicated by the fact 

 that the distillate is non-toxic, while the concentrate is more toxic 

 than untreated bog water. 



2. The colloid is reversible, because when obtained as solid 

 matter it is quickly redissolved on the addition of a volume of 

 cold water equal to the volume of bog water from which the solid 

 was originally obtained. 



3. The solid material of bog water when obtained in the dry 

 form is a granular powder. Since the distillate from which this 

 was obtained as a residue is not colloidal, and since a solution 

 having colloidal properties can be obtained by redissolving this 

 solid matter, it seems that it is the material that is in the colloidal 

 state. 



4. Bog water has elsewhere (15) been shown to have a slightly 

 lower surface tension than that of pure water. To what extent 

 this may be due to the presence of the colloid has not been deter- 

 mined. 



5. No means has been found of testing the swelHng of this 

 colloid, since it goes into solution so readily. 



6. No evidence has been found that the colloids increase the 

 viscosity of the water. 



