IN CEYLON. 
459 
humidity of the air. During the rest of the year when 
the air is very damp the number of deciduous species 
which become leafless is very small, and when the maximum 
humidity obtains from June to October the number of 
leafless species is at the minimum. 
The main points may therefore be briefly summarized in 
order to see which factor or factors are most instrumental 
in the phenomena under consideration. 
In the following table the monthly humidity, temperature, 
and rainfall at Peradeniya are given, and also a column 
showing the number of species which are either leafless or 
passing through some stage of defoliation during each 
month in the same district (c/, plate XXIX.). 
Month. 
Rainfall in 
Inches. 
Mean Monthly ^apfratur^ 
Humidity. ^XenS’ 
Number of Spe¬ 
cies, Leafless or 
undergoing 
Defoliation. 
January ., 
.. 4-75 
77 
73-2 
37 
February ., 
.. 237 
71 
75-0 
47 
March 
.. 3-48 
71 
77-3 
45 
April 
.. 7-59 
77 
77-5 
24 
May 
.. 5‘95 
... ‘ 78 
78*6 
10 
J une 
,. 9*11 
81 
... 75*5 
5 
July 
,. 6-85 
81 
74-9 
3 
August 
. 5-74 
... * 81 
74*9 
3 
September 
5*69 
80 
74*9 
2 
October .. 
10-99 
82 
75-2 
5 
November 
10*69 
79 
75-3 
9 
December.. 
. 8-95 
81 
73-4 
24 
It is in the combined effect of rainfall and atmospheric 
humidity that one can discern the principal agent in con¬ 
nection with foliar phenomena, in various parts of the tropics. 
The relative humidity of the air can be correlated with the 
amount of moisture lost by transpiration, and on the rain¬ 
fall depends the supply of water to make good that lost by 
the leaves. Both factors are therefore of great importance 
in connection with leaf-fall and foliar renewal. At a given 
place the increase in atmospheric humidity usually follows 
or accompanies that of the rainfall, and during a period of 
drought the humidity is correspondingly reduced. 
