[Proc. Rot. Soc. Victoria. 27 (N.S.), Pt. H., 1914]. 



Art. XV.— Bitter Pit and Sensitivity of Apples to Poisons, 

 An Answer to Prof. A. J. Ewart. 



BY 



H. G. BREIDAHL, B.Sc. 



AND 



A. C. H. ROTHERA, M.A, D.Sc. 



[Read 8tli October, 1914]. 



This opportunity has kindly been given us of replying to a paper 

 by Prof. A. J. Ewart, appearing in the Proceedings of this Society, 

 Vol. XXVI., p. 228, March, 1914, in which he criticises a paper by 

 R. H. Greenwood and A. C. H. Rothera, forming portion of the 

 Second Progress Report, issued by Mr. D. McAlpine. 



The position briefly is this : 



A theory that Bitter Pit might be due to poisoning of certam 

 cell groups in the apple was put forward by Dr. Jean White, and 

 strenuously supported by Prof. Ewart. This theory included the 

 statement that the apple cells of the areas affected with pit have 

 their diastatic enzymes destroyed — or inhibited — by the poison be- 

 fore the cells themselves are killed. It is logical, if this be so, to 

 attempt to show that bitter pit tissue contains some poison capable 

 of inhibiting diastatic action, and Greenwood and Rothera searched 

 first for such a poison in a soluble form, second in an insoluble 

 form. They were unable to get any evidence of inhibition, their 

 results either showing no effect, or in the case of malt diastase an 

 acceleration with both normal pulp and pitted material. This 

 acceleration was assigned to the beneficial effect which traces of 

 organic acids exert upon malt diastase, which explanation is still 

 held to be the correct one for this }-esult. since it naturally accounts 

 for the slightly greater acceleration produced by healthy pulp cells 

 than by ])itter pit, and also for the greater retardation of ptyalin 

 (wliicli is injui'ed by slight acidity), by the foi-mer than tlie latter. 



Against these expevimental results Prof. Ewart raises various 

 criticisms. 



His fir.st is a complete denial. He writes : " On repeating these 

 experiments with filtered solutions of malt diastase dissolved in 

 distilled water. I am alik' to give them emphatic contradiction. 

 Prolonged contact with pounded apple pulp, boiled or unboiled. 



