June, 1913.] 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’ theory 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 zymogens 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, trvpsino- 
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 (1908) 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 particular 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 
