Apr. 1894.] BOTANICAL SOCIETY OF EDINBURGH! 207 



The amount of oxygen ahsorhcd and retained by the seeds 

 varied very much, and indefinitely, in the different experi- 

 ments. Of the nine double results recorded, five are in 

 favour of light, two in favour of obscurity, and in two 

 equality was observed. 



On comparing the mean rate of increase in tlie carbonic 

 anhydride produced in favour of light, as determined by 

 this series of experiments, with the rate obtained in the 

 first series of experiments (where the carbonic anhydride 

 was weighed), it will be at once seen that it is rather more 

 than twice as great, and is, moreover, in the opposite direc- 

 tion. That is to say, in the first series of experiments an 

 excess of carbonic anhydride was produced in favour of 

 obscurity, and in the second series a greater excess of 

 carbonic anhydride was produced in favour of light. I 

 €an only account for this discrepancy in the results in the 

 following way : — 



In the first series of experiments a larger number of 

 seeds was employed ; these were confined in a narrow 

 tube, through which air was slowly aspirated. It is 

 evident that the air present in the tube must be con- 

 taminated to a small extent with the carbonic anhydride 

 produced by the germinating seeds. On calculating the 

 amount of this contamination, from the quantities of air 

 aspirated and carbonic anhydride excreted, it was found 

 to vary from 0*58 per cent, to 1'26 per cent, during the 

 different experiments. It is possible that the influence of 

 light on the seeds in the exposed tube, in presence of this 

 small quantity of carbonic anhydride, may have tended, by 

 its partial decomposition, to diminish the observed amount 

 of carbonic anhydride excreted, though the results, when 

 compared with the degree of contamination in each experi- 

 ment, do not show any corresponding variation in the 



