﻿432 



BOTANICAL GAZETTE 



Similar results were obtained in the oxidation of the naturally 

 occurring chromogens, although they cannot be stated in as definite 

 a form. Equal amounts (25 gm. of fresh material) of tissue of 

 apple, of potato, and of the stems of Vicia Faba were each crushed 

 in 100 cc. of water and filtered rapidly. Enough of the standard 

 permanganate was then added to each solution to give the first 

 appearance of the chromogen color. Table II indicates the amounts 

 of permanganate required and the amounts of oxygen which they 

 represent. 



TABLE II 













75Xl0 -6 



Apple 



Vicia Faba stems 



These results indicate that the amount of oxidation necessary 

 to produce the colored appearance in either the ordinary oxidase 

 reagents or in the plant chromogens is exceedingly small. This, 

 however, does not indicate that the oxidases are capable of produ- 

 cing only a small amount of reaction, for after the color appears 

 the oxidation may continue without necessarily changing the 

 color. 



These observations also clearly indicate that the amount of 

 oxidation necessary to produce a color in the various reagents varies 

 over a wide range. But by this very simple method the different 

 reagents may be calibrated so that the effects of the oxidases may be 

 measured, and the oxidation necessary to produce a change of color 

 in the presence of oxidases may be expressed in grams of oxygen 

 required. 



Laboratory of Plant Physiology 

 Harvard University 



