MULBERRY-DWARF TROUBLES IN JAPAN. 



203 



The above tables clearly show that the reserve materials in 

 the roots and stems undergo a very remarkable change during 

 the development of leaves in spring. The greater part is trans- 

 ported to the growing parts, especially to the leaves, and there 

 used partly for the formation of new cells and partly for the 

 respiration process. Thus we see that in summer, when the leaves 

 are in full growth, the roots and steins contain only very little 

 reserve materials, but in autumn, the assimilation products formed 

 in the leaves, again come down to the stems and roots and are 

 there stored up to provide for future growth. Such a process 

 is quite natural and every plant follows the same course ; 

 still there obtains a great difference in different plants, as to 

 the quantity of the reserve materials and the rapidity of their 

 migration. Some plants store up large quantities, while others 

 contain very little. These differences must naturally exist not 

 only among plants of different species, but also among different 

 plants of the same species. 



The reserve materials in plants are generally fats, carbohy- 

 drates and nitrogen compounds, but in the case of the mulberry, 

 fats seem to play no important role. 



It is a remarkable fact that non-albuminous nitrogen com- 

 pounds (most probably amido-compounds) are contained as 

 reserve materials in large quantities, corresponding, as they do, 

 to nearly one-half of the total nitrogen. 



As amido-compounds are soluble in water and easily trans- 

 portable they may be conveniently used during the energetic 

 development of the plant. Here we must not forget that, not 

 the whole of the nitrogen compounds contained in the stems and 

 roots, serves as reserve materials, but only some portions of them 

 are capable of transformation ; since there is a not inconsider- 

 able quantity of nitrogen in the form of insoluble compounds 



The greater part of the reserve carbohydrates in the mul- 

 berry consists of starch, the presence of which may be easily 

 demonstrated under the microscope. Further, we can easily 

 prove the migration of starch during development without the 

 aid of quantitative analysis. Thus, if we examine the bark of stems 

 or roots under the microscope, we shall soon discover that in 

 winter and in early spring, the bark is remarkably rich in starch 

 grains, which, on the application of iodine, cover the entire field 

 with violet spots. But in summer, when the leaves arc fully 



