18 Alfred J. Eivavt: 



organisms, the starch grains are dissolved away. If metallic 

 poisons are responsible for these defects, their j^resence shuuld be 

 capable of demonstration by direct analysis, since potatoes are 

 much less sensitive to metallic poisons than are apples. Organic 

 poisons are, however, also a possible cause, for it is now well known 

 that the infertility to crops of certain peaty and other soils is due 

 to the presence of traces of organic poisons of tlie iiatui'e of phenols, 

 or creosote-like combinations. * 



The late Dr. Rothera carried out some experiments in the direc- 

 tion of endeavouring to produce bitter pit symptoms by the direct 

 absorption of dilute solutions of metallic jjoisons. Cut leafy 

 branches bearing fruit were placed in solutions of copper sulphate 

 and mercuric chloride of strengths varying from 1 in 100,000 to 

 1 in 600,000. The results obtained were negative. The tests, how- 

 ever, only lasted a fortnight, and were discontinued on account of 

 the slirivelling of the apples. The latter is due to the rapid 

 blocking of the cut surface preventing the absorption of water (and 

 poison). If the experinient is carried out differently by driving in 

 the poisonous solution under a head of 5 or 6 feet of water or 

 roughly one-sixth of an atmosphere positive results are easily 

 obtained in a few days, and although the browning usually takes 

 place along the veins, it is often strikingly reminiscent of bitter pit. 

 When these tests were performed in the unripe starch stage, the 

 apple always died before all the starch grains had dissolved in the 

 unpoisohed pulp cells, but I have already shown that if dilute 

 poisons are injected into young apples while on the tree, although 

 most of the treated apples usually fall, some remain and ripen on 

 the tree. These show bitter pit areas at the points injected and 

 these areas show every sign of normal bitter pit, including the 

 presence of starch grains in brown cells, Avhile the surrounding 

 healthy tissue contains no starch. 



A second test carried out by Rothera was by watering apple trees 

 with solutions of copper sulphate of 1 in 100,000 strength. 



The following results were obtained : — 



Yield. Pitt<<l. ° Pitted. 



Counted by Mr. IMc Alpine— 



Gravenstein - ]00 - 8 - 8 



Jonathan - - 164 - 1(5 - 9.7 



Coimted by Dr. Rothera — 



Charles Eoss - 48 - 10 - .'20.8 



Mr. McAlpine, however, states that the trees used were previously 

 liable to Bitter Pit. Why such trees were selected for the test is 

 difficult to say. To be conclusive the tests would need to be repeated 



