16 CIRCULAR 112, BUREAU OF PLANT INDUSTRY. 



with a fungicide prevents the former disease, but has no effect upon 

 the latter. It seems evident, therefore, that these two diseases are 

 distinct. 



Microscopic examinations of the affected tissues failed to reveal 

 the presence of any organism to which the disease could be attributed. 

 The cells involved resemble similarly located cells in cases of ' l bitter- 

 pit," or "Baldwin spot," in which that disease extends to the 

 surface of the apple. Bitter-pit differs from this disease, how- 

 ever, in that it is essentially a disease of the fleshy portion of the 

 fruit, often reaching to the core without affecting the skin, while the 

 "Jonathan spot" is usually little more than skin deep. The writers 

 consider the disease a physiological one, but as in the case of the 

 bitter-pit the cause is at present obscure. 



SUMMARY OF CONCLUSIONS. 



The investigations conducted by the writers seem to warrant the 

 following conclusions : 



(1) The Jonathan fruit-spot of the apple is due neither to spraying 

 with arsenate of lead nor to a specific organism. 



(2) It is probably a physiological trouble, falling in the same 

 category as the bitter-pit or Baldwin spot. 



(3) Early picking, prompt cold storage, and immediate consump- 

 tion of the fruit after removal from storage, will largely obviate 

 losses from the disease. 



[Cir. 112] 



