Brooks : The Fruit Spot of apples 433 





time they bear a close resemblance to the earliest stages of Black 

 Rot. Sections of the spots show that the hypodermal parenchyma 

 is affected from the first. Only in late stages does the browning 

 and shrinking extend to the large isodiametric cells of the apple 

 tissue. On the green surfaces the spots may become sunken before 

 harvest time, but the depressions are due to a lack of growth and 

 not to any shrinking of the flesh. A minute black speck usually 

 develops at the lenticel and smaller specks may often be seen at a 

 radial distance of one to three millimeters from the first. A micro- 

 scopic study of the underlying tissue shows that the cell walls of 

 the hypodermal parenchyma and transitional tissue are abnormally 

 thickened and that this thickening is especially prominent in certain 

 groups of brown cells that underlie the surface specks (plate 30, 

 figures 1, 2). In the center of these brown cell-masses one often 

 finds small pockets produced by the collapse of one or two cells. 

 In cellar storage the red spots become badly browned and sunken. 

 The green spots may take a similar course but in many cases there 

 is no marked change in their surface appearance. Under such 

 circumstances, however, one often finds that the disease is spread- 

 ing deeper into the tissue and that a pocket is being developed as 



PLATE 



The development of the spots depends greatly upon seasonal 

 and storage conditions. When the weather is damp and foggy 

 during the last weeks before harvesting, the spots on the red fruit 

 surfaces develop rapidly and become black and sunken before the 

 ff uit is removed from the tree. After gathering, the spots develop 

 m <>st rapidly on apples placed in boxes and barrels in cellar 

 storage. On apples placed immediately in cold storage the spots 

 m ake but little or no development. When apples are stored in a 

 warm, dry place and wither rapidly, brown spots are not de- 

 veloped. On the withered fruit the green spots often stand above 



surrounding portions, forming smooth green elevations that 

 are >n marked contrast with the yellow withered skin of the apple. 

 Like the Fruit Pit the Fruit Spot is often accompanied by a 

 downing of the vascular tissue. In late stages of the Fruit Spot 

 0ne s °metimes finds minute elevations at the lenticels in the center 

 of the brown sunken areas. These seem to furnish the only dis- 

 t,r >guishing characteristic between the Fruit Spot and Fruit Pit at 



the 



this 



stage. 



