CHARACTERISTICS OF BITTER PIT. 



11 



In Canada it was described in 1896 by Craig (22) as a " Dry Rot " of apples, and in England, 

 in the Gardeners' Chronicle of 1905, as "Apple Brown Spot." It seems to have been recognised 

 in Germany even as early as 1869, where it is known under the names of " Stippen," " Stippflecke," 

 and " Stippigwerden," indicating the pitting or stippling characteristic of the disease. 



In France it is known under the names of " Points bruns de la chair " (brown spots of the 

 flesh), and "Liege" (cork disease), with reference to the cork-like nature of the cells. 



The spotting of the fruit was no doubt frequently noticed by the orchardist, without being 

 considered definite enough and of sufficient importance to be recorded, and such local names were 

 applied as "measles" and "small-pox." 



NAKED-EYE CHARACTERS. 

 This is a disease of "pip" fruits, such as apple, pear, and quince, but for our present 

 purpose, the description will be confined to the apple. As the name indicates, there are usually 

 pits or depressions on the skin, and these hollows on the outside represent a corresponding 

 shrivelling or shrinking of the tissue inside. These depressions are numerous, and mostly on the 

 upper half of the apple. They may be confined to one side, or extend all round, and sometimes 

 reach to within an inch or so of the stalk. There is always a small area surrounding the stalk 

 free from the "pits." (Frontispiece.) They vary in size from mere dots up to one-eighth of an 

 inch in diameter, but they may run into one another, and form larger depressions. They are 

 generally roundish in outline, and the colour varies from a pale to a dark green, but on the same 

 apple they may assume a ruddy brown or a dark brown tint, The outside appearance, however, 

 is very variable, according to the stage of the disease. There may be no external indication 

 whatever, and it is only when you begin to eat the apple, and find it' bitter to the taste, and with 

 brown spots through it, that you realize the presence of bitter pit. But, as a rule, there are surface 

 indications. There may be just the slightest sign of an indentation, with no change in the colour 

 of the skin, or there may be a regular depression, with the skin there of a deeper green, then they 

 may become of a pale or dark-brown colour, until almost the entire surface of the apple is covered 

 with them. When a transverse section is made, internal brown spots may occur all round, 

 generally beneath the skin, with occasional spots scattered through the flesh, even reaching to the 

 boundary of the core. These spots are at first of a pale brown, and gradually turn a darker brown. 

 This brown tissue is generally dry, and of a loose and spongy texture, as if honeycombed. The 

 brown streaks in the flesh not connected with the surface pits are associated with the fibro- 

 vascular bundles. (Plates I. and II.) 



MICROSCOPIC CHARACTERS OF THE BROWN SPOTS. 

 These are the naked-eye characters of this disease, but if sections of the brown spots are 

 examined under the microscope, the cells are seen to be collapsed, with their walls toughened, and 

 if observed when the fruit is ripe, and the starch has been converted into sugar, the dead brown 

 cells contain numerous starch-granules. (Figs. 24, 25.) Of course, at an earlier stage, both 

 diseased and healthy cells contain starch. A peculiarity of this disease is that the fruit may not 

 show any external sign while still on the tree, but only after it has been in store for a longer or 

 shorter period. However, with us its development is common while the fruit is still attached to 

 the tree, and I have seen over 90 per cent, of the Prince Bismarck variety of apples badly affected 

 on the trees. 



The browning of the tissue has to be explained, as well as the large cavities in it, while the 

 surrounding healthy pulp is white, and it is most important to determine the changes which have 

 actually taken place. Thus, Sorauer (85) assumes that at the time when the fruit was swelling, 

 the cell-walls of the brown tissue had already become corhj, and, being incapable of further 

 expansion, the cavities in the tissue thus arose. But, as we shall see immediately, there is no 

 evidence of corky cell-walls. 



