320 Mr. A. J. Wilmott. Experimental Researches on 



assimilation capacity, with given strengths of bicarbonate, the ideal plan 

 would be, after preliminary experiments, to be able to present results giving 

 identical rates in a pair of selected solutions. Only a short time was, however, 

 available for the experimental work of this section, and the equivalence of 

 pairs of solutions had to be deduced by rule of three. For the soundness 

 of this procedure it must first be demonstrated that in a series of CO2 

 solutions of different strengths the rate of bubbling is directly proportional 

 to the concentration within the range that it is proposed to iise ; the same 

 proportionality should also be demonstrated for a series of bicarbonate 

 concentrations. These two demonstrations are given in the next two sections, 

 and the direct comparisons of CO2 and bicarbonate follow in a third section. 



(A) Experiments luith Carbonic Acid Solutions of Different Strengths. 



The results of the first experiment, in which the solution in the plant 

 chamber was changed frequently for others of different strengths, is given in 

 fig. 12. Each new solution shows the " initial CO2 diffusion effect "* leading 

 to a steady rate. This steady rate in each solution would be maintained for 



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2S 



20 



a. 



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ceTictation 

 - and 



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Fig. 12. — Bubble rates of Callitriche in a quickly daaoged series of CO2 solutions, 

 showing the initial CO2 diffusion effect before the bubbling settles down to a steady 

 rate. Strong light (= 10) ; temperature 17° C. 



Fig. 13. — Similar series to that in fig. 12, but with a weak light of 3'o units. Light now 

 limiting in the first two solutions. 



* See Part I, p. 310. 



