CHANGES ACCOMPANYING BREAKING OF REST PERIOD 33 



From this it must be concluded that the brown color was produced 

 by a reaction in the tissue. Heating prevents the production of the 

 color, and etherization favors it in unheated material. So far as 

 known, the oxidising ferments are the responsible agents. 



In determining how the agents used to break the rest period 

 influenced the oxidases, the cortex was scraped from the treated 

 twigs, ground up and exposed to the air for a short time. The color 

 changes were then noted. 



It is difficult to express quantitatively and accurately the varia- 

 tions in the shades of brown which were observed. Hence the 

 results of these observations are not given in tabular form. Careful 

 notes were made in all cases, and these are summarized in the follow- 

 ing paragraphs. 



In general, the treated material was not much deeper in color, 

 than untreated material in the early part of the dormant period. 

 Somewhat later the color differences were very striking, the treated 

 cortex being the deeper brown in practically every case. Toward 

 the close of the season the differences again became less noticeable, 

 and in the last few weeks differences could seldom be observed. At 

 this time of the year (March) the untreated material showed a 

 much darker brown in a given period of time than at the beginning 

 of the dormant season. In all cases where the material had been 

 heated to 100 C. for a short time, it remained greenish for more 

 than twenty-four hours. The brown color of unheated cortex 

 appeared soon after grinding. The deeper the color, the sooner it 

 appeared on the mass of tissue exposed to air. 



The ground ash cortex did not become brown either with or 

 without treatment. Different varieties of the apple showed varia- 

 tions in their behavior as far as coloration of the treated and un- 

 treated tissue was concerned. For example, material from the 

 Woodmanse was usually somewhat lighter in color than Ben Hur; 

 and King David generally gave the darkest coloration. Just what 

 caused these variations is not definitely known. Cortex from 

 weak twigs usually remained green for a longer time than cortex 

 from vigorous twigs taken from the same tree. Cortex from similar 

 twigs taken from similar trees of the same variety, showed about 

 the same shade of brown when the same treatments were given. 



The character and kind of treatment used affected the coloration 

 to some extent, e.g., injured material became deeper brown than 

 dry material. The cortex from twigs bathed in alcohol remained 

 a deeper green than etherized material. In general the more 

 intense the treatment, if not too intense, the deeper the brown 



