﻿I 70 



BOTANICAL GAZETTE 



[march 



from the plants to the water outside. The experiment as a 

 whole shows that no necessarily valid conclusions can be drawn 

 as to the stimulation of the respiration of Elodea with HgCl^, 

 even using the purest distilled water. 



The significance of the observations on the influence of Zn 

 and Cu was immediately in doubt. Acting on the suggestion 

 derived from the similar effect of HgCU on tap water and on 

 distilled water after the Elodea had stood in it, I used tap water 

 with Zn and Cu, so that the reaction, if any, should be more con- 

 siderable. 



TABLE XXV. 

 March 9. Action of Zn and Cu on tap water. 



Time 



Experiment 



Control 



12 :23-l :23 



1:23 



Vl 



1000 



- ZnSO^ in exp. 



0.005 



1 : 23-2 :25 



2:25 Exp. stopped. 

 2:25-3:25 



M 



1000 



bottle. 



M 



lOOOO 



0.150 



CuSO^ in con 



o.oio 



CuSO^incon, 

 0.052 



trol bottle. 

 0.645 



These results approach what I got with the same *' stimu- 

 lants" with Elodea in the water, 



A test of the apparent action of AgNOg on the respiration 

 was followed immediately by one with tap water. 



TABLE XXVI. 

 May I. Test of AgNOg. 



Time 



8:44-1:45 



I :45 



M 



AgNO 



m 



Experiment 



0.042 



exp. bottle 



This is just near enough to the 

 result with Elodea to rob the lat- 

 ter result of significance as to the 



respiration. 



In another test of the action 

 of AgNO^ on tap water, the 

 water was boiled and cooled with 



40000 



I : 45-2 : 45 



2:45-3:45 ,. 



Tap water then used, with lout any plants. 

 5:34-7:04 



N 



0.130 

 0.095 



nyplam 



0.037 



7:04 



1 0000 



7 :04-8 :04 



AgNOo in bottle 



0.080 



a stream of COg-free air passing 

 through it. It was poured into 

 another bottle and then dosed 

 with AgNO 3, which drove off only 

 a trace of CO^. The difference 

 between this and previous expert- 



