398 
Journal of Agricultural Research 
Vol. II, No. s 
lines, representing the oxidase activities of the curly-dwarf foliage, run 
at a higher mean level than the continuous lines, which represent the 
oxidase activities of the healthy foliage. The differences will be brought 
out in a mathematical form in a latter part of this paper. 
To get a clear idea of the striking differences in the rate and extent of 
growth existing between the healthy and the diseased plants, the re¬ 
sults showing these differences are represented graphically in figure 21. 
The ages of the plants are represented on the abscissae, the mean weight 
Fig. 21.—Curve showing the differences in rate and extent of growth between healthy and diseased 
plants, 
of the shoots on the ordinates. The continuous line represents the 
growth of the healthy plants, the broken line that of the diseased ones. 
The difference in weight of the two types of potato plants of the same 
age is strikingly apparent. The diseased plants made an average growth 
of only about one-eighth of the growth of the normal plants. 
The fluctuations in the curve representing the rate of growth of curly- 
dwarf shoots are to be expected when the complex nature of the disease 
is considered. The diseased plants used for experimentation, although 
showing the typical symptoms, differed greatly in size, as is shown in 
figure 21, in color, and also in the shape which they assumed on account 
of the inhibition of growth. 
