Brooks : The Fruit Spot of apples 431 







surface of the apple. These depressions are somewhat hemispheri- 

 cal in shape and have the appearance of bruises. At this stage 

 the spots are not brown and often show no difference in color from 

 the surrounding surface of the apple. They may be a deeper red 

 than the adjacent tissue when occurring on the colored portion of 

 the apple and a darker green when on the lighter parts. Later they 

 begin to take on a brown tint, but at first this seems to show 

 through from rather deeply seated tissue and not to arise from any 

 discoloration of the epidermal or immediately underlying cells. 

 Sections of such spots show that this is the case, and that the 

 browning and the shrinking of the cells occur in the pulp of the fruit 

 and in the tissue that is transitional between it and the hypodermal 

 parenchyma. Later the surface cells also become dark brown. 

 The epidermis may be smooth and apparently unbroken in both 

 early and late stages. As the disease advances spots situated near 

 each other often become confluent, developing into one large spot. 

 In all such cases examined it was found that the original spots 

 were closely connected with one vascular branch. The writer has 

 been unable to detect a bitter taste in the browned tissue of the 

 fruit pits. 



Internal browning of tissue. — The surface spotting is often ac- 

 companied by browning of the tissue immediately surrounding the 

 vascular bundles. Upon cutting such an apple one sees numer- 

 ous apparently isolated brown spots. Further study shows that 

 these are not isolated but are in reality continuous strands of brown 

 tissue surrounding the vascular bundles. The portion of the vas- 

 cular system that is most commonly affected is that lying within 

 fifteen millimeters of the surface of the apple (plate 31, figure 

 The surface spots often occur without the internal browning 

 a ud also the internal browning may occur unaccompanied by any 



evident surface derangement. 



Cause and occurrence. — Microscopical examinations of fruit 

 Pits have given no indication of the presence of fungi or bacteria. 

 Br own tissue from the surface pits and from the more deeply 

 seated vascular regions has been transferred to various culture 

 "*dia but always without securing bacterial or fungous growth. 

 B °th the fruit pit and the internal browning are evidently abnormal 

 Physiological conditions. Their nature and location would indi- 



