June, 1918.] The Mosaic Disease of the Tomato. 167 



relation between the active and reserve enzyme, for the regener- 

 ation occurs in dead cells; no new supply of zymogen is manu- 

 factured, neither in the expressed juice nor in the functionless or 

 dead cells. 



Although Woods' theor}^ attempted to explain the behavior of 

 these enzymes, his views are not now quite in accord with the 

 rapidly changing ideas concerning this class of enzymes. He 

 does not attempt to explain their mode of action upon inoculation 

 in the host. No statements are made as to the means by which a 

 minute drop of juice injected in the proper place brings about such 

 transformations as are observed in mosaic disease. It is well 

 known that z\miogens exist for enzyme processes in which hy- 

 drolytic actions occur. Starling (1902) has shown that trypsin 

 of the pancreatic juice is actually secreted as a zymogen, trypsino- 

 gen, which lacks proteoclastic power, but possesses other properties 

 similar to those of trypsin itself. The oxidizing enzymes seem to 

 be far more complex and the intimate and intricate mechanism of 

 this group is not so well understood. There seems to be no satis- 

 factory explanation of the increased abundance of oxidizing 

 enzymes in diseased areas of leaves. The methods employed by 

 Woods (1899) for determining the presence of these oxidases were 

 simply colormetric tests, since the reactions accelerated by the 

 juice involve a change in color. Various indicators were used, of 

 which tincuture of guaiacum was most satisfactory. He desig- 

 nated those enzymes which gave a reaction directly with guaiacum, 

 as oxidases, those requiring an addition of hydrogen peroxide, 

 peroxidases. This classification is no longer used, see Bayliss 

 (1911, p. 109). Woods' tests were simply qualitative and cannot 

 be depended upon for various reasons as Foa (190S) points out. 

 Guaiac resin for example, assumes a blue color on oxidation, but 

 loses it when the process of oxidation is continued beyond a certain 

 stage. He also gives one to understand that oxidases and per- 

 oxidases are not always constant in their mode of action. A 

 certain result in the oxidation of any partictdar substance gives no 

 ground for generalization as to the catylitic power in general. 



Up to the present time no manometric analysis of plants 

 affected with mosaic disease seems to have been made. Such 

 methods have been devised and employed by Mathews (1909) in 

 the Spontaneous Oxidation of Sugars and Bunzel (1912, 1913) on 

 the curly-top of beets. It is obvious that such an analysis would 

 bring out the exact relationships which exists between these 

 enzymes, in healthy and diseased leaves or in any specific areas of 

 such leaves. 



Preventive Measures. 



Various measures have been suggested by scientists and 

 growers for the purpose of controlling or preventing the appearance 

 of mosaic disease. Most of the remedies for tobacco mosaic are 



