Bitter Pit in Ajyples. 393 



examined. The resistance of the apple as a whole to the ex- 

 ternal application of poison will depend upon its age, upon 

 the development of the cuticle and bloom, and upon the variety 

 of apple. 



In regard to the influence of age, the inherent resistance of 

 the pulp cells progressively decreases as the apple becomes adult. 

 In cool storage the sensitivity of apples to poison is only slightly 

 increased even after five months. After removal from cool stor- 

 age, however, the sensitivity rapidly increases after the first 

 week or two. 



Apples with an unbroken skin and good bloom may be im- 

 mersed in poisonous solutions of far greater concentration than 

 that required to kill the pulp cells. An adult apple is in 

 fact a most delicate but marvellously well-protected mechanism. 

 The young apple is less well-protected externally, but its pulp 

 cells have a greater inherent resistance to poison. A young 

 apple could, in fact, absorb sufficient poison to kill its cells when 

 adult without being affected at first while it was young. 



For the above reasons it is difficult to make exact comparisons 

 between different varieties, but with apples of equal age, the 

 sensitivity of the pulp cells to metallic poisons is in the follow- 

 ing order: — Five Crown, Jonathan, Scarlet Nonpareil, Roke- 

 wood, Rome Beauty, Yates' Pippin^, the last-named being- 

 much more resistant than the first. There are, however, natural- 

 ly some exceptions with specific poisons. Thus Rokewoods and 

 Yates' Pippins appear to be less sensitive to lead than Jona- 

 thans, and Yates' Pippins were also much less sensitive to copper 

 sulphate. Similarly brucine nitrate was apparently slightly more 

 poisonous to Rome Beauties than strychnine sulphate, but with 

 Five Crowns this was reversed. Rokewood and Rome Beauties 

 showed almost exactly the same sensitivity to citric acid, but not 

 to more active poisons. 



A verv interestino- fact noticed was that as a o-eneral rule 

 with minimal concentrations of all poisons, the poisonous action 

 usually disappears first from the more exposed side of the apples 

 as indicated by the colour of the skin. Thus the prepared 



1 Yates Pippin appears to be comparatively iuuimiie to bitter pit under natural condit- 

 ions, at least Dr. White found no apples of this variety affected by it in any of the 

 orchards examined by her. 



14 



