235 



BOTANICAL GAZETTE 



[APRIL 



the tests was 0.05 per cent., that is, the filtrate obtained from the solu- 

 tion of o. 20^"" of the enzyme powder in 200" of water, filtered and 

 then diluted one-half by the addition of an equal volume of the toxic 

 solution. During 5 hours' incubation at 40° C, o.i'''' of neutral 

 acetate in 4'''^ of water remains neutral. 



In this test, as in several that follow, it was observed that while 

 there was sediment in each of the vials containing boiled enzyme, the 

 vials containing the unboiled solutions were at the close of the incuba- 

 tion entirely clear and free from sediment. There is no doubt there- 

 fore that partial inhibition of the enzyme is possible and actually 

 occurs in the absence of any precipitation whatever. In this table 

 we note that the uninhibited activity of the enzyme is expressed by 

 0.18'^'^. The most concentrated solutions of the sahs reduce this to 

 o . 04 for potassium and to o. 03 for sodium. The amount of inhibition 

 is therefore very considerable, and yet there was no precipitation even 

 after an incubation period of 5 hours at 40'' C. In this test the 

 nitrates of sodium and of potassium are certainly to be regarded as 

 equitoxic. 



TABLE II: Potassium^ sodium, and lithium in contemporaneous test 



POTASSIUM 



Enzyme 0.05 per cent. Incubation 4 hours at 45 C. 



So far as this particular test is concerned, it can hardly be said that 

 the salts are equitoxic. On the other hand, it cannot be positively 



