Bitter Pit in Apples. 377 



growth, and if this kept puce with the accumulation of poison 

 the latter might remain in an almost infinitesimal concentration, 

 and yet produce a pronounced external or internal effect. This 

 is, of course, a suggestion only, but one that seems worthy of 

 consideration, particularly in regard to certain abnormal or 

 cancerous growths, not due to specific disease organisms. 



Hypodermic injections of poison. 



In order to determine the actual sensitivity of the pulp 

 cells to poison, it is necessary to be sure that the poison pene- 

 trates freely. Hence experiments Avere made by using a fine 

 hypodermic syringe to inject small amounts of very dilute solu- 

 tions of poison into the pulp of sound apples. Blank injections 

 and injections with tap water and distilled water produced 

 even after six weeks no spreading from the point or line of 

 puncture (the needle and liquid were sterilised before each 

 puncture), but the surface became slightly depressed around 

 each puncture, owing to the increased evaporation wheie the 

 cuticle was broken. Injections of approximately one-tenth of 

 a cc, of 1 per 100,000 solutions of copper, mercury and lead 

 after six weeks looked superficially no different to blank injec- 

 tions, but except in a few cases where the needle evidently be- 

 came blocked in puncturing, well-developed bitter pit areas were 

 present around or at the base of the punctures having a dia- 

 meter of 3 to 5 mm., and in the largest of these areas a few 

 cells packed with starch grains were found. 



However carefully the puncturing is done, the loose apple 

 pulp cells block the needle more or less, so that it is impossible 

 to inject accurately measured quantities. Owing to the physical 

 differences between apple pulp and animal tissue, this method 

 is in fact not suitable for exact quantitative investigations in 

 this particular case, and hence was abandoned in favour of a 

 more exact and controllable modus operandi. 



The actual sensitivity of the pulp cells of 

 apples to poison. 



The method used was to remove around the equator of each 

 apple fragments of the cuticle approximately a millimetre square 



