232 
CHARLES O. APPLEMAN 
difference in either the catalase or oxidase activity in the varieties 
showing a difference in rate of respiration. A varietal influence on 
both catalase and oxidase was soon discovered, although it is much 
greater in some cases than in others. The most striking difference 
was noted in the case of McCormick and Carman No. i. Both vari- 
eties were under identical storage conditions for nearly two months 
prior to the date of experiment and both bore sprouts of practically 
the same vigor as determined by length and total weight. The 
sprouts were removed just before the measurement of the rate of 
respiration. The Carman No. i tubers respired more rapidly than the 
McCormick tubers. The catalase activity in the two varieties was 
strikingly correlated with respiration. On the other hand, the oxidase 
activity was four times greater in the McCormick tubers. Tables 
IX and X show typical experiments with these two varieties. 
Summary and Conclusions 
The introduction contains a statement of the fundamental differ- 
ence between physiological oxidation as it occurs in respiration and 
ordinary combustion of organic substances in air. This is followed 
by a brief discussion of oxygen activators and carriers in plants and 
the difficulties encountered in assigning to the oxidases a role in 
respiration. 
The important literature pertaining to catalase in its relation to 
respiration is reviewed. 
The task was a quantitative study of the relation of both oxidase 
and catalase activity to intensity of respiration. Potato tubers 
seemed especially favorable material for a study of this kind since 
respiration in these tubers is greatly accelerated by various artificial 
treatments and is subject to fluctuation under natural conditions, as 
greening, sprouting, etc. The rate of respiration also varies in different 
parts of the same tuber and in tubers of different varieties. Besides, 
potato tubers contain very active oxidases and catalase. The modi- 
fication of the intensity of respiration in these tubers was determined 
and at the same time measurements were made of both the oxidase 
and catalase activity in the juice. The data seem to justify the 
following conclusions: 
I. The oxidase content in potato juice gives no indication of the 
intensity of respiration in the tubers. In other words, there is no 
