142 EXPERIMENT STATION. [Jan. 



to stand tor a short time to thoroughly drain, and the nitrate 

 was treated with dilute acetic acid 1 : 4. The filtrate was 

 greenish in color, and when acted upon by the acetic acid a 

 flocculent precipitate was obtained which was also greenish in 

 color, — whether due to impurities or pulp is a question. 



A portion of until tered juice was also saved for treatment. 

 A diluted solution of commercial hydrogen peroxide (H 2 2 , 

 containing 3 per cent, of pure H 2 2 ) was treated with a small 

 amount of the residue obtained from the first nitration. An 

 abundant evolution of oxygen gas resulted, showing that cata- 

 lase was present, in insoluble form, at least. The insoluble 

 catalase has been called by Loew a catalase. As no other 

 known enzyme will break down hydrogen peroxide (H 2 2 ) in 

 this manner, it is safe to say that catalase was present. 



The first filtrate was added to a diluted solution of hydrogen 

 peroxide, and a somewhat smaller amount of oxygen relatively 

 was evolved. To the precipitate obtained by the acidification 

 and precipitation brought about by the action of the acetic acid 

 on the second filtrate was also added a diluted solution of 

 hydrogen peroxide, and the amount of oxygen evolved was 

 very small, only traces of the gas being found. As this pre- 

 cipitate contained presumably all the soluble catalase found in 

 the leaf, it was shown that the tomato leaf contained very little 

 soluble catalase. The explanation for the greater amount 

 liberated from the first filtrate is that the filter was so coarse 

 that some of the pulp containing the insoluble form passed 

 through into the filtrate, producing an energetic evolution of 

 oxygen. The soluble form of catalase is known and is de- 

 scribed by Loew as /s catalase. 



In the normal condition the tomato leaf contains a large 

 amount of the insoluble form and only traces of the soluble 

 form. 



After finding that catalase was present in the normal tomato 

 leaf, a number of leaves of plants affected with the mosaic 

 disease were treated in a similar manner, to determine whether 

 the presence or absence of this enzyme had anything to do 

 with this disease. The leaves of the diseased plants were 

 treated in exactly the same manner as the leaves of the normal 

 plants, so that there might be no chance for error due to treat- 

 ment of the leaves. 



