1909] DACHNOWSKI— BOG TOXINS 397 



Several facts seem to be clearly brought out in the above data. A 

 comparison of the toxicity figures of bog water collected at intervals 

 during the year indicates that the amount of toxic substances in 

 solution differs very appreciably within the year. In all cases the 

 physiological studies show that the adsorbing substances actually 

 remove definite quantities of bog toxins. In contrasting the efficiency 

 of the various amounts of adsorbents used, the important facts at the 

 outset are these. Different physiological phases result from the pro- 

 gressive increase of an adsorbing substance. The bog-water solution, 

 fatal in its effect at some seasons, gives an increase in growth-rate 

 when adsorption removes a sufficient amount of the toxic ingredient. 

 The effect is virtually one of dilution. Doubling of the amount of 

 the adsorbent brings the growth-rate into a physiological phase 

 marked by a greater functional activity. Further addition and its 

 consequent further dilution in toxicity carries with it a corresponding 

 intensification in growth-rate. The appearance of the plants, espe- 

 cially in the development of the root system, follows the transpira- 

 tion figures very closely (see 5, figs. 1, 4-5, p. 135). Stimulation and 

 tolerance rise to a maximum. But with successively larger amounts 

 of adsorbent, the optimum rate of transpiration can be neither 

 increased nor maintained. It falls off, regularly and rapidly at first, 

 subsequently less rapidly, until the effect of the solution is practically 

 that of distilled water (13). Greater dilution and consequent 

 increase in rate of transpiration does not express therefore the whole 

 truth. Other and less injurious substances are also adsorbed; and 

 the rate of transpiration is seen to be the product of a coordination 

 of factors (1). In bog water with very slight toxicity, the course of 

 the experiment shows that the maximum acceleration phase deviates 

 y er y sensibly toward the growth-rate approximated in the control 

 >•£•> the untreated bog water. 



On account of the difference in size of particles, there naturally 

 follows a corresponding difference in the amount of adsorption. 

 Compared with kaolin, calcium carbonate, carborundum, and 

 carbon (as lampblack or humus), the adsorptive power of quartz 

 ■ relatively low. It will be seen that the optimum rate of transpira- 

 tion of the tenth day, in solutions 3 to 8, Table IV, is soon succeeded 

 D . v a minimum. This is due to the action of toxic substances still 



