MULBERRY-DWARF TROUBLES IN TAPAN. 



269 



regions contained, in spite of the imperfect developement of 

 chlorophyll, always many starch granules. He found that 

 the oxidizing enzymes can inhibit the diastatic action, and by 

 making the saccharification of the starch in the cells much more 

 difficult than in the healthy leaves, prevent the migration of 

 it into other parts of the plants. 1 To prove the correctness of 

 this view, he prepared a concentrated solution of tobacco 

 oxidase, mixed it together with a small quantity of " Taka- 

 diastase " or malt extract with some diluted starch paste and 

 kept the mixture at 45°C. At the same time a control mixture 

 was prepared, in which the oxidase solution was previously 

 boiled for a few minutes ; After thirty minutes a very remarkable 

 difference was observed. In the former case starch was not at 

 all saccharified, erythrodextrin being the final product, while in 

 the latter (control case) the entire starch was saccharified. Such 

 phenomena may also occur in the diseased leaves. Beijeiinck 2 

 supposes that there exists a so-called " Contagium vivum 

 fluidum" in the extracted and filtered juice of the tobacco 

 leaves suffering from the mosaic disease. This fluid contains 

 no visible organism, still it produces the same disease by 

 injection. Woods rejects this view and thinks that the so 

 called " contagium vivum fluidum " is identical with the 

 oxidizing enzymes. He made several experiments to produce 

 the disease by injecting solutions of oxidizing enzymes into 

 the healthy plants and succeeded in some cases, though not 

 always. 



The question why oxidizing enzymes are produced in an 

 abnormally large quantity in the diseased leaves has not yet 

 been satisfactorily answered, but it is very probable that the 

 decrease of vital activity and the deficiency of nutriment in the 

 cells has some intimate relation with their production. Woods 

 succeeded in producting the mosaic disease artificially by 

 cutting back rapidly growing tobacco plants. Loew also holds 

 the view that partial starvation can cause an increase of these 



1 Dr. Smith also observed an increase of the amount of the oxidizing enzymes in the 

 diseased leaves in the " peach yellow "-disease. 



1 Science. N. S. Vol. XI., No. 262, page, (January 5, 1900). 



Beijerinck. Verhandelingen der Koninklijke Akademie van Wetenschappen to 

 Amsterdan. Tweede sect. Deel. VI. 1898, No. 5. 



