384 
Journal of Agricultural Research 
Vol. II, No. 5 
the curve generally begins. The juice from the plant collected on the 
sixty-seventh day seems unusually rich in oxidases. If the points ob¬ 
tained from the data on this plant were discarded, the curves would be all 
quite regular, with the exception of those corresponding to the oxidation 
of hydrochinone and of some of the cresols. To show what types of 
Fig. 8.—Curve showing oxidation of phloridzin in the presence of the juice of potato foliage. 
curves would be obtained by elimination of the points obtained for 
the sixty-seventh day of growth, which point seems irregular, the 
adjacent points on both sides of the “sixty-seventh-day point’’ 
are connected with relatively thin lines to complete the curves; the 
initial fall and the final rise thus become very apparent and clear-cut. 
Fig. 9.—Curve showing oxidation of o-cresol in the presence of the juice of potato foliage. 
The curves, of course, are not smooth. This is to be expected when it 
is considered that there are numerous factors influencing the physiological 
condition of the plants. Differences in the nature of the seed, of the soil, 
and many other factors probably influence the development of the plant 
qualitatively as well as quantitatively. 
