246 



BOTANICAL GAZETTE 



[APRIL 



TABLE XVI 



Relative toxicity with varying concextrations of the enzyme 



Copper and zinc in contemporaneous test 



COPPER 



m 



Control 



Enzyme 



In crease 



2048 



0. 27 

 0.42 

 0.77 



2.90 



0.32 



0.46 

 0.80 



2.90 



0.05 

 0.04 

 0.03 

 00 



1024 



'^12 



2=:6. 



128 



00 





^^ * ^^ ^^ 



ZINC 



2048 

 1024 



256 

 128 



Enzyme o. 10 per cent. Incubation 5 hours at 40 C. 



In Tables IX, XI, and XII, copper and zinc have the same point of 

 total inhibition, namely m/1024. In those tests the concentration of 

 the enzyme was 0.05 per cent. Here when the concentration of the 

 enzyme is doubled the relative toxicity is changed. The point of total 



TABLE XVII 



COPPER 



m 



Control 



2048 

 1024 



256 

 128 



0.50 

 0.80 



1950 

 2.90 



Enzyme 



0.47 



0-55 

 0-85 



2.90. 



Increase 



0.14 



0.05 

 0.05 

 0.00 

 0.00 



ZINC 



2048 

 1024 



512 



256 



128 



o 



o 



o 



I 



3 



32 



50 



87 

 70 



40 



0.47 

 0.65 

 1.02 

 1.80 



3-5<^ 



0.15 

 0.15 

 o. 10 



O.IO 



Enzyme 0.15 per cent. Incubation 5 hours at 40 C. 



7256 and for zinc mf 



In Table XVII 



where the concentration of the enzyme is still higher, the difiference in 

 toxicity is more pronounced. 



In the work on ethyl butyrate, cadmium, cobalt, and zinc were 



