DAVENPORT: THE ROLE OF WATER IN GROWTH. 81 
The fact that water plays so important a part in the development 
of organisms has an important bearing upon the interpretation of 
curves of growth. These curves, whether made for animals or 
plants, have a decided resemblance (Figs. 4, 5, 6a). They are all 
constructed on this plan : the abscissae indicate times or ages ; 
the ordinates, the absolute size (weight or volume) at a given 
time. The ordinates do not show, therefore, the growth or incre¬ 
ment in the strict sense of the word. In order to show this 
increment we might transform our curve of frog growth into 
another, in which the ordinates are proportional to the absolute 
daily increment (Fig. 7). This curve is seen to be, within the 
limits of the series, a rapidly ascending one. 
Fig. 7. Curve of daily absolute increments in weight (in milligrams) of tadpoles of 
from 1 to 80 days after hatching. 
Professor Minot has, however, suggested that such a curve as 
this does not give a true insight into the vigor of growth at the 
