318 Mr, A. J. Wilmott. Experimental Researches on 



clialk plant alone gives a positive reaction. It increased its rate fourfold, 

 while the three shoots from the tub showed no increase. It will be seen 

 that, after two hours in acid, the rate of bubbling in A, B, and B' has fallen 

 to about half. It was not made clear to what extent possible escape of CO2 

 from the solution, reduction of CO2 concentration by assimilation, and 

 injurious efTect of the acid, were responsible for this big fall, as there was 

 no opportunity of doing further experiments on this point. It is interesting 

 to note that the extra source of CO2 available for the chalk plant has come 

 to an end, and that its rate also has fallen to half the original value. The 

 termination of the tempoiary acid-chalk increase ought to be investigated 

 further. 



Experiment Table. 



Elodea. 



Grown in rain water. 



From chalk stream. 



4 shoots 



A 



B 



B' 



C 





7-8 



18-3 



I -23 



85 -0 



Time. 



Kelative rates of bubbling. 



p.m. 











12.8: 



10-0 





10 -0 





12.10 





10 -0 







12.13 









10-0 



12.15 



10-0 





10 -0 





12.19 





10 







12.20 



4 c.c. N/10 HCl added to make acidity 0-0008 N. 



12.35 



10-8 









12.36 







10-2 



40 -0 



12.38 





11 -5 







1.5 



8-0 





8-8 





1.9 





10 





39 -2 



2.10 









5-2 



2.12 







6-1 





2.17 





5-8 







2.23 



5-5 









2.30 





6-3 





5-0 



2.35 



4-9 









Tlie effect of dosing the plant, as Treboux did, with a series of increasing 

 strengths of acid, is shown in fig. 10. In this case the first two increases of 

 acid each produced a marked rise in bubble rate, but with subsequent 

 increases the further rise diminishes until between E and F it is nil. That 

 the value here reached is not merely a light limit is shown by the greatly 

 increased rate in H when more CO2 is given. In fig. 11 the rates of bubbling 

 are plotted against concentration of acid, and it is seen that a linearly 



