MAKKET DISEASES OF APPLES, PEAKS, QUIN^CES 27 



Shriveling, when slight, is accompanied by a reduction chiefly in 

 size; when severe, by a marked reduction in both size and weight. 



Apples that have been severely frozen frequently show noticeably 

 sunken spots which may be a quarter of an inch deep or more, with 

 a superficial diameter about equal to their depth. In virtually all 

 cases these sunken spots develop at places that were bruised while 

 the apple was still frozen. (See Bruises, p. 16.) 



Apples that have been both bruised and frozen while in transit by 

 rail frequently show flattened areas 1% to 2 inches in diameter that 

 are somewhat sunken and soft toward the center and have a dull- 

 brown or slate color over most or all of the surface (pi. 10, A, B). 

 The transit bruises described on page 16 are smaller in diameter, 

 flat instead of sunken, the skin covering them is not slate colored, 

 and the flesh beneath is firm. 



It should be remembered, however, that during a short exposure 

 to an air temperature several degrees below freezing considerable 

 ice may form within the tissues and yet produce little or no effect 

 that could be diagnosed as freezing injury. 



INTEENAL APPEAEANCE 



Usually the best indications of freezing injury are found by exam- 

 ining a cross section of the fruit. If a cut is made crosswise through 

 the middle of an apple that has not been frozen, there will be seen, 

 about halfway between the center and the outside, 10 small dots, 

 the natural color of which in most varieties is green or yellowish 

 green, but in the Winesap, Esopus Spitzenburg, and some other va- 

 rieties is occasionally tinged with red. These dots are the cut ends 

 of the main fibro vascular bundles of the apple, which are connected 

 with numerous but less conspicuous threadlike fibers extending 

 throughout the flesh. The whole network, including the large 

 bundles, constitutes the vascular (or foocl-and-water-conducting) sys- 

 tem of the fruit, and, so long as the fruit remains on the tree, is in 

 direct connection with a similar system in the twigs and branches. 



When freezing occurs the cells of the vascular system are usually 

 the first to be affected, especially if the freezing takes place rapidly ; 

 and they may be the only ones so affected. In cross section this 

 injury is shown by a brown discoloration of the 10 large main bundles 



(pi. 10, C), the color being visible evidence that the cells have been 

 frozen to death. Similar browning may occur in the smaller strands 

 through the flesh and in the core tissue; it is frequently restricted 

 to one side of the apple because of lower temperature on that side. 

 In more extreme cases all of the tissues may be affected; the flesh 

 then shows a solid color throughout which varies from bright golden 

 brown to darker brown or almost black, depending on the variety of 

 the apple and the severity and freshness of the freezing injury 



(pi. 10, D). These browned areas in whatever tissue found usually 

 have a water-soaked appearance and in milder injury are translucent. 



EFFECT OF FREEZING AND THAWING 



It is generally believed that frozen apples are injured less by 

 gradual than by rapid thawing. Careful investigation of the sub- 

 ject has shown, however, (1) that apples frozen rapidly when thawed 



