CEYLON. 
451 
a large percentage of our endemic and indigenous species are 
deciduous during this dry hot period ; and (2) that the greater 
number of our introduced species obtained from such widely 
different climates as Brazil, Java, Australia, America, Africa, 
West Indies, Ac., undergo defoliation from January to March. 
These facts suggest that reduction of transpiration is perhaps 
one of the objects in view. During these months when the 
air is usually dry and the temperature high, the leaves of 
many evergreen plants begin to flag during midday and only 
expand in the late evening and early morning. Throughout 
this period the leaves transpire copiously and probably 
thus allow the greater part of the water supplied by the 
roots to escape. The temperature, two feet below the ground, 
rises to 83° F., and during this period the water supply to 
the superficial root system is somewhat limited. Under 
these conditions on© can see the advantage of, and in certain 
cases almost the necessity for, a reduction in transpiration 
such as may be achieved by passing through a leafless phase. 
' The actual variation in temperature—one to two feet below 
ground—is not very great, but the maximum during 
certain months is high, and the water supply to the feeding 
rootlets at two feet below ground must be appreciably 
affected. 
The following are the temperatures in Fahrenheit from 
January to May, 1903, recorded at the Experiment Station, 
Peradeniya:— 
Jan. Feb. March. April. May. 
One foot below 
ground ... 73 to78 ... 73to 78 ... 76 to81 ... 79 to 83 ... 76to 83 
Two feet below 
ground ... 74 to79 ... 75 to78 ... 77to80 ... 80to 82 ... 78 to82 
Having shown that the leafless phase is associated with 
our dry hot period and that the conditions of air and soil 
are such as to necessitate a reduction in transpiration during 
the drought, the question of the unanimity between the 
foliar activities of the different species during this period 
can be studied. 
