MULBERRY-DWARF TROUBLES IN JAPAN. 1 87 



in the leaves is a clear evidence of the retardation of vital 

 activity. 



The deficiency of nitrogen compounds in the diseased leaves 

 is not caused by an insufficient supply of nitrogen manures, since 

 the disease is always rampant on fertile soils and on soils treat- 

 ed with soluble manures. The principal cause of the retarda- 

 tion of vital activity must be either the cutting of the stems in the 

 growing season, or the exhaustion of reserve materials in the 

 roots and stems by excessive drain of the leaves. This question 

 will be discussed fully in the next chapter. As regards the ash 

 contents, we find on the average less in the diseased leaves, but 

 sometimes there are exceptions, so that we can not draw 

 any definite conclusion on this point. In the ash of the dis- 

 eased leaves we generally find less silica, sulphuric acid and phos- 

 phoric acid and more lime and magnesia, but the difference is not 

 very regular. At any rate, we may conclude that the disease is 

 not caused by the deficiency of some special mineral nutriments 

 in the soil, and the difference in the ash ingredients may be simply 

 an effect of the disease. 



The diseased stems contain also less fibres, but the percent- 

 age of nitrogen is apparently higher ; this may be explained by 

 the fact that in the healthy stems the development of fibres is 

 enormous, in consequence of which the percentage of nitrogen 

 seems apparently lowered. There must of course be remarkable 

 difference in the absolute quantity of nitrogen contained in one 

 stem. No regular difference is found in the ash ingredients of 

 the diseased stems. 



Chapter II. On the Reserve Materials of the Mulberry 

 Tree and their Relation to the Disease. 



In this chapter, the reserve materials of the mulberry tree, 

 their migration, and their relation to cutting is fully discussed. 

 The samples used for analysis were all taken from the mulberry 

 farm of the Tokyo Sericultural Experiment Station at Nishigahara. 

 Three varieties, Takasuke, Tsuruta, and Jumonji, were selected 

 for this purpose. They were all under the same treatment in the 

 same farm, and eight years old (low cutting). Five plants of 



