THE BITTER-ROT FUNGUS. 19 



THE DISEASED APPLE. 



An apple affected with the bitter rot or ripe rot is a most objection- 

 able fruit. The name of the disease is derived from the peculiar bitter 

 taste of the decayed tissues of the fruit which is noticed almost as soon 

 as the fungus has begun its growth in the cells. One observer (Alwood, 

 1894) states that this bitter taste is not always present. The partially 

 decayed fruit leaves a bitter taste in the mouth, resembling the after 

 effect of quinine, yet not quite the same. The bitterness increases as 

 the rot becomes more pronounced. The tissues of the apple are hard 

 and firm when first affected; the cells look somewhat watery and are 

 pale brown. As the rot advances the flesh of the apple softens and 

 turns darker in color, until at an advanced stage the whole tissue is 

 soft and mushy, very watery, and without any resemblance to the 

 original healthy tissue. Attention should be called to the fact that in 

 no case does the apple become as soft and mushy as it does when 

 affected with most other fruit-rotting fungi, for instance, the black 

 rot. The decay starts at the surface of the fruit and gradually extends 

 inward toward the core, making a sort of cone-shaped mass of dis- 

 eased tissue, as described above (figs. 2 and 3). 



During the early stages of the disease there is a marked accumula- 

 tion of starch around the affected spots, which calls to mind similar 

 phenomena described by Halsted (1898) for various leaf- spot fungi. 

 The cells of the apple tissue separate from one another as the disease 

 progresses. The middle lamella of the cells is dissolved by the fungus 

 hyphaB, but the cell walls themselves remain intact. 



THE BITTER-ROT FUNGUS. 



LIFE HISTORY ON APPLES. 



The spores of the bitter-rot fungus germinate on the apple fruit 

 when it is nearly ripe. In some cases the fungus has attacked apples 

 when the}^ were only three-fourths of an inch in diameter (Garman, 

 1893). which, however, may be regarded as exceptional. The hyphas 

 from germinating spores enter the apple and begin to grow in the 

 layer immediately under the epidermis. Whether the young hyphse 

 can pierce the uninjured epidermis of the apple seems to be a some- 

 what disputed point. In making infections of apple fruits in the lab^ 

 oratory it was found that the greatest numbers of successful infections 

 were obtained by puncturing the epidermis with a sterile needle and 

 then spraying the spores on to the broken epidermis. Clinton (1902) 

 states that the spores placed on unpunctured apples, "if successful," 

 brought about the rot two or three days later than when placed on 

 punctured fruits. It is probably true that the young hyphse can enter 

 through the unbroken skin, possibly through the stomates, but at the 



