I9I9] 



ROSE— BLISTER CANKER 



III 



agree well with those obtained without a shaking machine in show- 

 ing considerably greater oxidation by diseased than by healthy 

 bark. The ratio between the two, i .00:2.19, is larger than that 

 found previously (1.00:1.28), the difference probably being due 

 to dift'erences in drying or possibly to the shaking itself. 



T.\BLE II 



0.\ID.\TION OF PYROG.4LLOL BY HE.\LTHY AND DISEASED APPLE BARK; 

 S.4MPLES 3 AND 4; TEMPERATURE 27 0=^1.7° C. 



I 



In table III are summarized the results of an experiment to 

 test the oxidizing power of both diseased and healthy bark on 

 pyrocatechin, guaiacol, and benzidine. 



A comparison of the figures in table III with those in tables I 

 and II shows that diseased bark causes greater oxidation of pyro- 

 gallol, pyrocatechin, benzidine, and guaiacol than does healthy 

 bark, and that both tissues cause greater oxidation of the first 

 two reagents than of the last two. It is further shown by tables I 

 and III that the amount of oxidation increases slowly for several 

 days; in fact table III shows that it is practically doubled for all 

 the combinations, except those containing pyrocatechin, during 

 the 64-hour period following the 3 hours' shaking. This fact of 

 an increase of oxidation on standing was observed to a greater or 

 less degree with most of the bark material used in this work, and 

 is in direct contradiction to Bunzell's explicit and repeated 

 statement that oxidation in his apparatus comes to a definite end 

 after 3 or 4 hours' shaking. The only exceptions the writer has 



