Bitter Pit in Apples. 405 



more or less corky superficial scars, but never causes an appear- 

 ance of bitter pit in Jonathans, Five Crowns or Scarlet Non- 

 pareils. 



Pole-Evans' theory is apparently based upon the idea that the 

 stoppage of transpiration produces a sudden increase of pres- 

 sure, just as occurs when a stream of water floAving through a 

 hose pipe is blocked at the orifice. This is of course a funda- 

 mental misconception, since the osmotic pressure depends upon 

 the osmotic concentration of the cell sap which the plant is 

 able to control, and as soon as the hydrostatic pressure in the 

 cell balances the osmotic pressure, further absorption of water 

 ceases, 



Pole-Evans' theory was based upon the simple observation, 

 which is quite correct, that sections of bitter pit tissue commonly 

 show broken cell walls. The same is also shown in artificial 

 bitter pit tissue produced by poisoning. As the cells die and 

 shrivel, the walls become brittle, and being thin are easily 

 broken either by the general contraction or by the tearing of 

 the razor during the section cutting. ^ Natural bitter pits treated 

 with dilute potash and carefully teased out may sometimes not 

 show a single broken cell-wall, and the more carefully sections 

 are cut the fewer are the broken cell walls. Further, when 

 broken cell walls appear naturally in artificial bitter pits, they 

 usually occur at the boundary of the pit tissue and normal pulp 

 cells, the adherence of the former to the skin causing the 

 breaks when the shrivelling is pronounced. In lioth natural and 

 artificial bitter pits, any breaking of the cell walls follows instead 

 of precedes the formation of the pit. 



Dr. White then investigated the enzymes of apples affected 

 by bitter pit, and from her observations, came to the conclusion 

 that the non-solution of the starch grains which usually accom- 

 panies bitter pit could only be explained as a symptom of local 

 poisoning. She was able to detect the presence of lead in the 

 bitter pit tissue of apples from an orchard which had been 

 heavily sprayed with arsenate of lead^. The fact that bitter 

 pit may also occur in orchards which have never been sprayed 

 does not affect the theory that bitter pit is not a disease at all, 

 but a symptom of local poisoning. The two most trenchant 



1 Proc. Roy. Soc. of Victoria, 1911, p.l. 



