ROOT DISEASES 



141 



Root Diseases. — The crown gall (Fig. 87) is one of the very 

 common diseases of onr fniit and other trees, roses, berries and 

 many other plants. It is cansed by bacteria and appears as 

 abnormal c;rowths on the roots and sometimes on the trunk and 



Fig. 87. — Young tree with crown gall. 



branches. In some cases it does bnt little harm, but in, other 

 cases it reduces the vitality of the plants and in extreme cases 

 causes death. The so-called hairy root of the apple, pear and 

 quince is caused by the same organism. The roots of these dis- 



