406 Alfred J. Ewart: 



criticisms made to contest the statement that bitter pit could 

 ever be due to poisonous sprayino; materials were — (a), that if 

 so, it would occur most in the cup at the stalk end of the fruit, 

 and (b), that in the apples examined by Dr. White the lead 

 might have entered after the bitter pits were formed. In regard 

 to (a) the answer is simple. The stalk end is at first convex, and 

 the cup only develops as the fruit becomes adult. It is then 

 almost without exception covered by a more or less corky, pro- 

 tective, impermeable layer, and has few or no breathing pores 

 through which poisons could enter. The reply to (b) is given 

 by the experiments already detailed and to follow. 



The fact that poisonous sprays may affect the foliage is well 

 known, and it would be in the highest degree remarkable if 

 under no circumstances were any effects exercised on the fruits. 

 In 1902 Bain investigated the injurious action of copper fungi- 

 cides on peach foliage^. He found that penetration did not 

 necessarily take place through the stomata, and that the injury 

 might appear at some distance from the point where the drop 

 of spray material (Bordeaux mixture) was applied. Further, he 

 found that at first the production of starch was increased, and 

 that later signs of injury or death were shown. If the amount 

 of poison is sufficient, the dead cells will retain undissolved 

 starch grains. In other words, we have here a " bitter pit " of 

 foliage directly produced by poisonous sprays. Bain also found 

 that seedling apples were more sensitive to poisons than seedling 

 peaches, and were rapidly killed when a solution containing 

 0.0000075 gram molecules of copper sulphate per litre was 

 applied to their roots, 



G. Stone (Massachusetts' Station Report), found that during 

 1909 spraying with Bordeaux mixture caused noticeable injury 

 to apple foliage and fruit, and that arsenate of lead spraying 

 caused foliage burnin<r, especially on plum trees, but also on 

 maple and beech. 



W. N. Scott (Phytopatholooy, 1911, page 32) found that a 

 fruit spot of apples, particularly of Jonathan and Esopus, which 

 develops usually after picking, is dark brown, usually circular, 

 from :f to J inch or less in diameter, and slightly sunken with a 

 lenticel in the centre of each spot. It has been observed in 



1 Ajjric. Exper. Station, Univ. of Tennessee, vol. .\v., p. 21. 



