232 BOTANICAL GAZETTE [march 



slight increase in oxidation occurs. The higher hydrogen ion 

 concentration is probably the cause of the slight depression in 

 oxidation of the o.ioN strength of the salt. The slight increase 

 in oxidation of the lower concentrations suggests that phosphates 

 may increase oxidase activity, but the limited data are inconclusive. 

 It is interesting to note that Iwanoff (19) found that phosphates 

 raise the amount of respiration in living wheat seedlings. Zaleski 

 and Reinhard (33) found that disodium phosphate increases the 

 output of carbon dioxide from dried ground seeds, and that the 

 monobasic phosphate decreases it because of the acid reaction. 

 These authors also quote from the work of a student, Miss 

 Schklousky, who showed that phosphates increase the action of 

 peroxidases, and from work of another student, Miss Rosenberg, 

 who showed that phosphates stimulate the catalase activity of 

 different seeds. 



In the case of salts of organic acids and the carbonates, all 



more 



experiment 



when it is not. Examples of this are shown in table IV. The 

 effect of the salt is not merely additive, however, either here or in 

 the case of the carbonates, as is shown by the following: 



Oxidation of pyrogallol by bark and salt 



Tested separately Tested together 



(cm. of mercury rise) (cm. of mercury rise) 



K 2 C0 3 4.46 2.70 



K tartrate 2.15 1.53 



Na oxalate 1 . 88 1 . 60 



m 



Evidently when bark and salt are combined, there is some factor 

 at work which brings about a slower rate of oxidation than might 

 be expected. What this factor may be we have no means of 

 knowing as yet. Possibly it is the partial neutralization of the 

 hydroxyl ions of the salt by the acid of the bark. 



The question why salts vary so widely in the effect they have 

 on oxidation is not easily answered. If we consider only the 

 results with o . i N solutions, it seems clear, in the case of the car- 

 bonates, potassium dihydrogen phosphate, and the salts of organic 

 acids here reported, that increased oxidation in their presence is 

 due to the excess of hydroxyl ions they furnish; that is, by the 



