104 MASS. EXPERIMENT STATION BULLETIN 175. 



a significant fact that this excessive activity of oxidizing^ enzymes has 

 been more frequently noted in diseases of this character than in those 

 which are caused by bacteria or fungi. The reaction of the host is ap- 

 parently different in the latter case. 



BunzeP has noted that the oxidase activity varies with the age of the 

 plant in the curly dwarf disease of potato, reaching its greatest activity 

 when the plant growth ceases. 



The writer has also found this to be true for tobacco to a certain extent, 

 and always met with greater activities of the oxidases as the leaves were 

 approaching maturity. This was marked in the case of normal plants, 

 but not so much in the case of diseased leaves. 



In the writer's examinations of healthy and diseased tissue not only 

 qualitative colorimetric methods were employed, but also a simpHfied 

 Bunzel's oxidase apparatus was made use of. This has been found to be 

 the most satisfactory method for the quantitative estimation of oxidase 

 activity.^ 



A few of the quantitative results obtained are given in Table XI. 



Table XI. — Oxidase Activity in Normal and Mosaic Sap. 



[Manometer readings in centimeters of mercury. Bunzel apparatus mod.] 



It will be noticed that the mosaic sap is higher in total and average in every instance. 



For the qualitative determinations the usual guaiac test was employed. 

 The guaiac test for oxidases and peroxidases is too well known to require 



1 Bunzel. H. H.: Oxidases in Healthy and Curly Dwarf Potatoes. Jour. Agr. Research, Vol. 

 II.. 5. 373-404 (1914). 



2 Bunzel, H. H.: The Measurement of the Oxidase Content of Plant Juices. U. S. D. A., Bur. 

 Plant Ind.. Bui. No. 238 (1912). 



