MULBERRY-DWARF TROUBLES IN JAPAN. 



275 



being completely prevented. For this purpose, a healthy and 

 a diseased plant were selected. A portion of the leaves was 

 taken from each plant for control (a) (Oct. 11) while the entire 

 plants were then covered with a large black paper cylinder 

 and thus kept deprived of light for two weeks, when leaves 

 were again gathered (b). The iodine test gave the following 

 results : 



Nczumigaycshi (i) 



Ogon (Normal condition) 

 (Not kept in the dark) 



Healthy 



Diseased 

 (Healthy 



( Diseased 

 Healthy 

 Diseased 



very little 

 very much 

 Almost none 



very much 

 very little 



very much 



Almost none 



Almost none 



very much 



Thus even after two weeks in darkness, traces of starch 

 were still present, while in the healthy leaves, the starch 

 disappeared completely in one night. 



I have also endeavored to find out whether the migration 

 of nitrogenous compounds in the diseased leaves is also retarded 

 like that of starch. It is a well known fact that the nitrogen 

 salts absorbed from the soil, are converted chiefly in the leaves 

 into proteids. According to my observation 1 the synthesis of 

 proteids chiefly goes on in the leaves during the day time, 

 whereas during the night they arc again split up into soluble 

 amido-compounds which are transported to the other organs, 

 like starch is in the form of sugar. I have also observed that 

 in the young growing leaves the migration of these amido- 

 compounds during one night can clearly be shown by analysis ; 

 the absolute quantity of nitrogen in the leaves gathered in the 

 morning is considerably less than in the evening. As to the 

 mulberry tree my experiment was made a little too late in 

 the season, and the migration intensity was too weak to show 

 a sufficient difference after one night. Hence I adopted the 

 following way : In the late autumn, when the activity of 

 the cells decreased and the absorption of nitrogen compounds 

 became rather slow, a healthy and a diseased plant were 

 selected ; a portion of the leaves was taken from each plant 

 and dried directly in the air bath at 50°C, vvhile another 



1 Bulletin of the Coll. of Agriculture. Komaba, Tokyo. Vol. Ill, No. 3. 



