4bU WRIGHT : FOLIAR PERIODICITY 
A glance at the curve indicating the number of species 
whichare leafless or undergoing defoliation during each month 
shows that in February when the rainfall and humidity are at 
the minimum the defoliation of the species is most active, 
and the same conclusion holds good for the dry month 
of March. But in April the rainfall and humidity of the 
air increase considerably, and though the temperature is 
higher than in February or March, the number of trees under¬ 
going their leaf change is considerably reduced. Equally 
striking is the fact that from June to October the humidity 
is near the maximum, the rainfall is abundant, and the 
defoliation of the deciduous trees is at the minimum. A 
better or more complete comparison could not be desired to 
prove that in a climate like that at Peradeniya there is an 
increase m the defoliation or leafless stage of deciduous species 
during the dry period and a decrease during the hot moist or 
relatively cool and moist periods. 
In other parts 0 f the island snch as Nuwara Eliya and 
Hakgala there is a coincidence between high hnmidity and 
heavy rainfall and the prevalence of a more or less evergreen 
vegetation. At Mannar a low rainfall and high atmospheric 
humidity prevail, and there is an approximate similarity in 
the number of deciduous species to tw r> v y 
Ceylon, it may be concluded that (I) a high tern t^ 8 ° f 
the minimum 
rainfall are clearly assoc ated wi h i ^ 
hnmidity and rainfall arc more - * "" 
the year there is less agreement betweenT^ .“"Tf!"* 
activities; Where there is a wideTariatL ^ 
throughout the year there ia , * ln thes ® factors 
driest time of theycar - ‘he 
