Vegetable Assimilation and Respiration. 321 



a long time, but readings were not continued in this particular experiment 

 beyond the point necessary to determine what this steady rate was for each 

 solution ; for even thus the experiment occupied two hours. The final values 

 are given in fig. 14 plotted against CO2 concentration. They suffice to 

 demonstrate that the bubbling rate is directly proportional to the concentra- 

 tion. This is not a new point, so that no elaborate experiments were made. 

 Treboux demonstrated it, and it accords with the findings of Blackman and 

 Smith (1911) using CO2 analysis instead of bubble rates. It must be noted 

 in fig. 12 that one of the values, the rate in the solution believed to be 

 1'068 per cent. CO2, is quite out of proportion by some error or other, but it 

 was not thought worth while to repeat the series. In this experiment a 

 strong light (intensity = 10) was used, and the light was in excess throughout. 

 In the next series the light was reduced to 3'5 units, and a similar range of 

 strengths of CO2 was repeated. 



These results are set out as a time sequence in fig. 13. In the last two 

 strengths we have the same initial effects as with the strong light series, and 

 here CO2 is still limiting. In the first two strengths the CO2, however, is in 

 excess, and the light limiting, and after some irregularities the final rate is 



Fig. 14. — The final values adopted from figs. 12 and 13 are here plotted against 

 CO2 concentration. With weak light (3"5) the proportionality between concentra- 

 tion and bubble rate is cut ofi" at about 0'9 per cent. CO2 by the light 'factor, while 

 with strong light (= 10) this proportionality is continued through 1 the 'whole 

 series tried. 



