108 



and their relative retarding effects upon the oxidase tests. The 

 names are arranged in the order of the corresponding activities : 



Acceleration of Sucrose Inversion Retardation of Oxidase Test 

 HCl (greatest) HCl (greatest) 



H2SO4 H2SO4 



Citric acid Citric acid 



Acetic acid Acetic acid. 



Summary of General Conclusions 



1. The oxidases are of very wide distribution among the 

 flowering plants; peroxidases, especially, being present in about 

 seventy-five per cent, of all the specimens examined, while oxy- 

 genases (direct oxidases) are less widely distributed, being found 

 in one-half of the plants used. Catalase may be said to be 

 universally distributed, since there were only a few cases in which 

 it was not found. 



2. The leaves, stems, roots and food-storage organs of the 

 plants seemed to contain the greatest amounts of the oxidases. 

 The flowers and fruit were in many cases comparatively poor 

 in oxidases. In regard to the fruits this statement must be 

 qualified because dry seeds of somewhat uncertain age were 

 the only available material of certain species. 



3. Our experience with a great many parallel tests, using the 

 different oxidase reagents upon a great variety of vegetable 

 tissues show that all of the reagents seem to detect the same sub- 

 stance or substances, for if one reagent gave a positive test the 

 others generally acted in like manner. The phenolphthalin and 

 indo-phenol reagents gave positive results in more cases than the 

 others. This is undoubtedly due to their greater ease of oxi- 

 dation, for they are spontaneously oxidized by the air. 



4. It is probable that in the presence of acid juices in the plant 

 the latter does not form oxidases or else that they are immedi- 

 ately destroyed by the acid. It was shown that the inhibiting 

 effect of acids upon the action of oxidases seemed to be a func- 

 tion of the concentration of the hydrogen ions. 



5. Among plants the chromogens are found to the greatest 

 extent in certain orders such as the Liliales, Orchidales, Ranales, 

 and most frequently of all in the latex plants of the Convol- 



