ii8 



BOTANICAL GAZETTE 



[FEBRUARY 



greater oxidizing power. For example, when both kinds of bark 

 were brought to approximately the same hydrogen ion concentra- 

 tion by buffer no. 6, the final amount of oxidation (mercury rise) 

 for healthy bark was i .95 and for diseased 4 .48, the final Ph 3 .98 

 and 4 . 60 respectively. The total oxidase activity of the diseased 

 plant is the joint oxidase activity of the host and parasite, while 



Fig. 3. — Oxidation of mixtures of healthy bark, pyrogallol, and various buffer 

 solutions: A, after 3 hours; B, after 22 hours (19 hours without shaking); C, after 

 29 hours; D, after 48 hours; A, bark, pyrogallol, and buffer solutions as indicated by 

 numbers; B, initial P^; points of plotting marked by vertical broken lines. 



the oxidase activity of the healthy plant is that of the host alone. 

 This may account in part for the difference both in rate of activity 

 and in the Ph concentration at the time the action ceases. 



Nature of equilibrium reached. — Bunzell (13), in experi- 

 ments with potato peel powder, has obtained what he considers 

 evidence that "the activity of the plant powder is not paralyzed 

 by the products formed in the course of the reaction." He found 



