IOI 
Leaf Surface of Cucumis sativus . 
autocatalytic reaction formula will give a fair representation of the increase 
in linear dimensions of leaves. 
In the curve of increase in area (Fig. 5) the points lie very satisfactorily 
Fig. 4. Curves of increase in the linear dimensions of a leaf. 
round the smooth curve, which represents the curve of closest fit of the 
autocatalytic type. 
The phenomenon of the expansion of individual leaves is similar in all 
respects to the expansion of axial organs, and displays the same ‘ grand 
period’. This fact is clear from the S shape of the curves in Figs. 4 and 5, 
for if from these a curve were constructed showing the variation in the rate 
of expansion with increase in time, such a curve would have a maximum at 
