IN CEYLON. 463 
It remains to be shown how different species in Ceylon 
give evidence of their independence or dependence on 
external conditions. 
Internal Factors. 
The fact that very few species pass through a leafless 
period each year, and that many evergreens produce new 
leaf at all times of the year suggests that foliar periodicity is 
largely a question of the individual convenience of the plants 
and is influenced only slightly by the climatic environment. 
The differences in climatic conditions throughout the year 
at Peradeniya are apparently not such as to afford any great 
advantage to change of leaf during a specified period, and the 
majority of the plants therefore produce new leaf at the 
initiative of internal requirements. 
Out of a total number of 650 endemic and indigenous 
arborescent species, no less than 560 are evergreen, and the 
foliar periodicity of the evergreens is as irregular as it can 
be. There is not a month in the year when some of the 
species are not producing new leaf or shedding the old. 
The foliar renewal of the evergreens may take place annually, 
as in Mesua ferrea, bi-annually as with species of Diospyros, 
which produce very large quantities of new leaves at a 
particular time of the year are subject to periods of minor 
foliar activity during the rest of the year. The individual 
branches produce leaves at irregular intervals, apparently 
without any qoncord with the rest of the tree of winch they 
form a part. 
The seeond fact of significance is that the deciduous 
endemic and indigenous trees do not select the same time of 
the year for shedding their old leaves or for foliar repletion, 
and there is not a month in the year when the deciduous 
species are all in full leaf. This irregularity obtains though 
all the plants may be growing under the same climatic eondi- 
