442 



ELEMENTARY STUDIES IN BOTANY 



fruit is completely dried out, and such " mummies/' as they 

 are called, may be seen hanging on the trees. It should be 

 realized that these mummies are exceedingly dangerous, for 

 they are the chief source of infection the next year. Often 



infections are so late 

 that the disease is not 

 detected until after the 

 fruit is picked and 

 shipped, in which case 

 a lot of slightly specked 

 fruits when shipped 

 may arrive as mum- 

 mies or nearly so. 



Cankers. These are 

 diseases that arise in 

 connection with open 

 wounds, and are con- 

 spicuous in trees (Fig. 

 91). Some knowledge 

 of cankers is of great 

 practical importance in 

 the handling of forests 

 and orchards. As they 

 are wound diseases, it 

 is evident how the 

 parasite enters, and the 

 wounds are formed in 

 nature by storms, and 

 in cultivation by trimming and bruising. If the wound is 

 small, it may heal naturally ; but if it is large, it may remain 

 as an open wound, exposed to continuous infection. 



Bitter rot. This is a very destructive disease of apples 

 and other fruits, and is known wherever -apples are culti- 

 vated. It is recognized by the characteristic spot it forms 

 on apples. It is at first small, increases rapidly in size, turns 



FIG. 91. Canker on apple tree. After SORAUER. 



