226 MULBERRY-DwARF TROUBLES IN JAPAN. 



ently the deficiency of reserve materials can not be made good by 

 the nutriments absorbed from outside. For the same reason, 

 cutting in late autumn produces more cases of the disease than 

 cutting in early summer. Since the activity of plant cells is 

 already diminished in late autumn the development of new roots 

 must be more difficult. 



6. Micro-organisms are not the cause, because they are 

 not always present in the diseased plants. Further, the decay of 

 the roots of the diseased plants may be a secondary phenomenon, 

 since we can not understand why the disease is not observed 

 when the plants are left without cutting, or why the diseased 

 plants may even recover by being kept from cutting, for some 

 years. Shoots of the diseased plants may develop normally 

 when they are grafted on healthy roots or stems, or when they 

 are covered with earth and propagated by cutting. But there is 

 no doubt that the mirco-organisms have some accelerating in- 

 fluence upon the disease and at last cause the death of the 

 plants. 



7. As regards the methods for the prevention and cure of 

 the disease, we must leave them to future investigations, since 

 we have not succeeded in finding any that promises success. 



