2 Jean White : 



labour over unnecessary work. One of the most striking charac- 

 teristics of this disease is that it may occur in the interior, whilst 

 there are no external indications of its presence. As a rule, 

 however, the external surface of the fruit is marked with distinct 

 depressions of varying sizes, and of a dark green or, more com- 

 monly, a brown colour. The pitting is far more pronounced 

 on the calyx end of the fruit, though not always absolutely 

 conlined to it. 



Examination of the affected areas with a hand lens sometimes 

 shows lenticels situated in them, whilst in other cases no sign 

 of any such structure is apparent. Underneath these groups of 

 surface depressions are found groups of spong}^ brown cells 

 which adhere to the epidermis when this latter is pulled away 

 from a soft, decayed apple. 



As a rule apples which are badly affected with bitter pit 

 become rotten much earlier than the clean ones, and usually 

 the rotting occurs in a peculiar manner, the whole of the flesh 

 becoming converted into a soft brown pulp without any sign of 

 organisms or abrasions on the external surface of the fruit. 



Micposcopic Structure. 



Thin sections through the diseased areas show on microscopic 

 examination that in those pits which are visible on the exterior, 

 the cuticle and epidermic layers, together with from about 8 to 

 10 layers of the small thick-walled cells immediately underneath 

 the epidermis, do not appear to be affected. The first cells to 

 become metamorphosed are those situated in the vicinity of the 

 transition of the cells possessing small cavities to those possessing 

 relatively much larger ones. The diseased cells appear to be 

 slightly enlarged, irregular in shape, and nearly empty, and are 

 spongy in texture. The cell walls are discontinuous in places, 

 and in the late stages of pitting there is a holloAv space in the 

 centre of the area from which all sign of cells has disappeared. 



On treatment with aqueous solution of iodine numerous starch 

 grains are disclosed in the region of the cell walls of the affected 

 cells, whereas in the normal flesh when ripe no such starch 

 grains are visible. The majority of my observations and experi- 

 ments have been made on Anne Elisabeth apples, and specimens 



