239 



BOTANICAL GAZETTE 



[APRIL 



It may be that the zymolyte ethyl acetate tends to minimize the differ- 

 ence in relative toxicity as compared with the zymolyte ethyl butyrate. 

 While this is a plausible explanation, it has little value in the absence 

 of convincing evidence, and we cannot select the determining factor. 

 Why the variations in the different tests should be relatively so wide is 

 not understood, especially in view of the precautions to avoid error. ^ 

 The following test shows that barium is more toxic than lithium under 

 the same conditions as imposed in a contemporaneous test. This 

 emphasizes the apparent tendency of the barium group to exceed the 

 sodium group in toxicity, and such a conclusion is perhaps permissible 

 in view of all the results of this work and that on ethyl butyratej but 

 it would certainly be difficult to say how much more toxic. 



TABLE VII: Barium and lithium in contemporaneous test 



Enzyme 0.05 per cent. Incubation 5 hours at 40'' C. 



In the preceding tests it will be remembered that the salts themselves 

 are neutral in all the concentrations used, and that the acidity of the 

 reagent is quite uniformly the same for all the concentrations of a 

 given salt, and that the acidity of the control is the acidity of the 

 enzyme solution itself, as is indicated by the figure for ''Water" in the 

 control column. It is apparent that the highest saturation is required 



9 Possibly the enzyme solutions differed sufficiently to account for the discrepan- 

 cies. Then too, the insolubility of the zymolyte may have been responsible to some 

 extent. 



