Bitter Pit in Apples. 397 



partly to its displacing bases less readily in the protoplasm of 

 the pulp cells than sulphuric acid. Either the latter reason or 

 a greater ease of penetration may explain why citric acid appears 

 to be more poisonous than oxalic acid, or the oxalic acid 

 may be precipitated to some extent without injury resulting. 

 The almost innocuous character of calcium hydrate (limewater) 

 is due to the carbon dioxide from the respiring pulp cells 

 precipitating the calcium ions as chalk. 



It is worth noting in this respect that the order of toxicity 

 in the list above differs ver^- widely on a quantitative molecular 

 basis from what it would be in the case of an ordinary animal. 

 This is especially shown in the relative positions of the alka- 

 loids, and heavy metals, in the position of sulphuric acid, in 

 citric acid preceding oxalic, and in magnesium sulphate preced- 

 ing formaldehyde and ammonia. In animals, however, any 

 poison which injures one organ may cause the death of the whole 

 organism, whereas in plants, the effects of poisoning may be 

 quite localised, and the death of a leaf by poisoning may 

 not affect the plant more than the mere removal of the 

 leaf would do, while the death of a fruit killed by poison may 

 actually be of benefit to the mother plant, and economise its 

 food supplies. 



Naturally if both kation and anion are poisonous, a. salt may 

 be more poisonous than either of its ions applied singly. Thus 

 brucine is sparingly soluble in water, but a solution in water 

 only showed distinct signs of being poisonous to the pulp cells 

 of Jonathan and Rome Beauty apples in a concentration of 1 in 

 25,000, doubtfully so in the case of 1 per 100,000, and none at 

 all in the case of 1 per 1,000,000. The sulphate was, however, 

 feebly but distinctly poisonous down to concentrations of 1 per 

 100,000. 



Further, a mixture of poisonous salts may be less poisonous 

 than either salt singly. In some cases the reason for this is 

 obvious. For instance, a mixture of 303 cc, of 1 per 100,000 

 barium chlorate and 246 cc. of magnesium sulphate 1 per 

 100,000, is slightly less poisonous than the last solution applied 

 singly. This is simply because the barium is precipitated as the 

 insoluble sulphate, and the chlorate ions of the magnesium salt 

 remaining are less toxic than the sulphate ions. 



