MULBERRY-DWARF TROUBLES IN JAPAN. 217 



No case of the disease was found in the control plants, 

 which were not deprived of their leaves. See Plates XXXV- 

 XXXVI. 



The age of the plants, varietal peculiarities and other con- 

 ditions have a great influence upon the disease. 



It is a well known fact that in those provinces where silk- 

 worm culture was recently introduced, the disease is especially 

 prevalent, because in these provinces, the farmers try to get the 

 largest possible crop of the leaves from rather small farms, and 

 consequently, over-manuring and frequent picking of the leaves, 

 sometimes followed by cutting, is commonly practiced. Further, 

 those varieties such as Takasuke, Hosoye, etc., which grow rather 

 rapidly, are mostly preferred. Moreover, silkworm culture in 

 late summer or autumn is especially injurious for the mulberry, 

 since the leaves are taken off in autumn, and the assimilation 

 products in them to be utilized by the stems and roots for the 

 next year's growth, are neccessarily lost ; and thus the principal 

 cause of the wearing of the plants is brought about. 



One might suppose that by giving an excess of soluble 

 manures, the injurious effect of the frequent picking of the leaves 

 or of cutting, can be counterbalanced ; such a view is erroneous. 

 In the growing period, manuring does not directly nourish the 

 stems or roots ; the nutriments being all transported to the 

 growing parts, especially to the leaves ; and in late autumn, the 

 assimilation products in the leaves come down again to the roots 

 and stems and are stored there until the next spring. In the 

 growing period, the roots and stems merely serve as a passage for 

 the nutriments. Therefore if we cut off these over-grown plants 

 in the growing season, the new shoots will grow energetically and 

 the reserve materials must be rapidly exhausted, the disease 

 being the result. 



Here I shall cite one more example showing that the disease 

 is nothing but the result of the deficiency of the reserve materials. 

 Healthy and diseased plants in the same farm were cut on 

 August 30, and the new shoots coming from the diseased stems 

 showed distinct signs of the disease even in the earliest stage. 

 On October 15, the plants were cut down and analyzed, with 

 the following result : — 



