.42 Alfred J. Eivart: 



tory, and in spite of the high range of variation {<i.o-i to 8.11) seen» 

 to indicate that medium pruning produces the laigest amount of 

 bitter pit, and no pruning the least, whilst hard pruning is inter- 

 mediate. Nevertheless on page 81 of the Report medium pruning^ 

 is recommended as one means of reducing bitter pit. Medium 

 pruning tends to concentrate the sap on the fruits, and with it any 

 poisonous ingredients absorbed, while hard pruning tends towards 

 new Avood formation, and so diverts some of the sap from the 

 fruits. 



The interesting experiments with different stocks carried out hv 

 Mr. Quinn are not yet far enough advanced to enable any con- 

 clusions to be made, but grafting is not likely to affect the resist- 

 ance of the pulp cells of the gi-afted scions to poisons. 



The influence of cool storage on Bitter Pit. 



Since the resistance of the pulp cells to poison is greatly increased 

 at low temperatures, it is only to be expected that in cool storage 

 the development of bitter pit should be retarded or even stopped, 

 Avhen only minimal amounts of poison are present. If the starch 

 grains were undissolved, the low temperature would prevent or 

 delay the last stage of complete poisoning and tuining brown. If 

 the amount of poison i^i-esent is lelatively large, brown spots 

 may still appear in cool storage, but the amount will be reduced. 

 (Report pp. 103, 105.) The influence of cool storage is mainly con- 

 fined to preventing or delaying the onset of the later stages of 

 poisoning, such as death and collapse of the cells, the turning 

 brown and acquiring a more or less distinct bitter taste. It is. 

 Iiowever, precisely these changes which render affected apples un- 

 saleable. An apple in the incipient stages of bitter pit, though a 

 little less sweet, will be as edible as one not affected at all, and the 

 point may be once again emphasised that an apple may be com- 

 pletely poisoned with various metallic poisons and yet contain insuf- 

 ficient poison to produce any ])oisoning symj^toms or effects when 

 eaten. 



Conclusions. 



The evidence in favour of the poisoning theory of bitter pit 

 Itrought forward in the present and previous paper, may be briefly 

 recapitulated as followe : — 



It is possible by applying poison during the starch stage of 

 an apple to reproduce artificially every symptom of bitter pit. The 

 diastase ferment which is responsible for the normal solution of 



