Bitter Pit in A2')ples. 419 



shown when a toxic concentration is reached after the cells have 

 become packed with starch. This at first prevents ferment action, 

 and later kills the pulp cells. 



The first stage of bitter pit, namely, the presence of occasional 

 cells with starch grains which do not dissolve during ripening 

 in perfectly sound ripe apples, is apparently almost a normal 

 phenomenon whether the apples are froin sprayed or unspruyed 

 orchards. This is the result of their extraordinary sensitiveness 

 to traces of poisons. 



In such apples and in bitter pit apples from unsprayed 

 orchards the poison must be absorbed from the soil. The rela- 

 tive incidence of bitter pit in sprayed and unsprayed orchards 

 is a matter of great importance. If 90 per cent, occur in sprayed 

 and 10 or less in unsprayed orchards, the immediate problem is 

 to find a substance which will diminish the toxicity of spray 

 poisons to plants, while leaving them equally effective against 

 the insect pests which eat and digest the poisonous spray with 

 the plant tissues. 



Among such substances appear to be lime and citric acid, but 

 much more effective ones may be found. So far as ihe evidence 

 goes at present, bitter pit appears to be much more prevalent 

 in sprayed orchards than in ones which have never been sprayed 

 or had any poison applied to the soil. 



On the other hand if only a minority of cases of bitter pit 

 are directly or indirectly due to the use of poisonous sprays, 

 it will be necessary to find what poisons are absorbed from the 

 soil or subsoil, and what correctives can be applied to them. 

 This is a chemical problem of some difficulty, since the traces 

 of poison required to produce bitter pit symptoms in the pulp 

 cells of apples are almost infinitesimally small, and a number 

 of different poisons may be acting on different trees in the same 

 orchard. 



On three points, however, it may, I think, be stated with 

 confidence that we are on a solid bed rock of established fact, 

 namely, that bitter pit is, strictly speaking, not a disease at 

 all, but is a symptom of local poisoning produced in the sensi- 

 tive pulp cells of the apples, that more than one poison may 

 produce it, and that such poisons may be derived from more 

 than one source. 



