144 BOTANICAL GAZETTE [February 



is attacked by the fungus the greater is its catalase activity, and 

 that catalase activity in part is in indirect ratio to oxidase activity. 



10. Microchemical tests indicate, for diseased bark, a partial 

 disintegration of cellulose, a disappearance of cyanogenic glucoside, 

 and a lower content of starch, calcium oxalate, and tannins. 



11. Macrochemical analyses show that diseased bark has a 

 higher percentage of dry matter, lipoids, alcohol-water-insoluble 

 residue, and total nitrogen, but a lower percentage of alcohol-water- 

 soluble material than healthy bark. The percentage of carbo- 

 hydrates in both tissues seems to be about the same. Differences 

 in tannin content are definite but not large. Sound healthy bark 

 contains more than diseased bark and diseased bark more than 

 dead bark from the surface of the canker. 



12. The greater oxidase activity of diseased bark is probably 

 due to the combined activity of the oxidases of fungus and host, 

 lower acidity, and possibly to a greater degree of dispersion of the 

 oxidizing agent. The lower tannin content of diseased bark may 

 also be a contributing factor. 



The writer wishes to acknowledge his indebtedness to 

 Dr. William Crocker, Dr. F. C. Koch, and Dr. Sophia H. 

 EcKERSON for valuable suggestions and criticism during the course 

 of the investigation. Thanks are due to Dr. Paul Evans of the 

 Missouri State Fruit Experiment Station for bark material used 

 in the experiments. 



U.S. Department of Agriculture 

 Washington, D.C. 



LITERATURE CITED 



1. Allard, H. a.. Some properties of the virus of the mosaic disease of 

 tobacco. Jour. Agri. Research 6:649-674. 1916. 



2. Appleman, Charles O., Some observations on catalase. Bot. Gaz. 

 50:182-192. 1910. 



3. Atkins, W. R. G., Recent researches in plant physiology. London. 1916. 



4. Bach, — , and Chodat, O. R., Untersuchungen liber die Rolle der Peroxyde 

 in der Chemie der lebenden Zelle: IV, tJber Peroxydase Ber. Deutsch. 

 Chem. Gesell. 36:600-605. 1903. 



5. Battelli, F., and Stern, L., Die Oxydationsfermente. Ergeb. Physiol. 

 12:96-268. 1912. 



