WRIGHT : FOLIAR PERIODICITY 
dealing with the leafless phase and the importance of the 
climatic factors. 
In a tropical district like Peradeniya the foliar periodicity 
may be determined by internal and external factors, and 
each species must be considered separately. The more 
equable the climate in different parts of Ceylon the more 
conspicuously will the internal forces operate, and the 
more independent they will be of climatic influences. My 
statement at the British Association Meeting of 1902 that 
botanists desirous of studying the internal forces in plant 
life should select a tropical country other than Ceylon is 
still supported by the further results of this investigation. 
In a general way it maybe said that the nearer to the tropics 
the more the personal equation influences the phenomena 
of plant life, and as we pass from the equator—north or 
south—the less the power of the internal forces and greater 
the power of climate in determining the periodicity of 
plant life. 
Even in those parts of the tropics where there are definite 
seasons, the phenomena appear to be the ontcome of climatic 
and individual forces. In more eqnable tropical zones, with 
the nnnimum climatic variation, the plant phenomena are 
almost entirely determined by the individual requirements. 
Respecting the effect of internal and external factors the 
main points may be summarized as follows :— 
(1) The foliar periodicity of deciduous trees is inherent in 
tropical and temperate zones since it is observable in ail these 
thi 1. K tropical the climatic conditions 
he larger ,s the number of arborescent epeeiee and the 
larger is the proportion ot the evergreen trees in the 
(Of. British and Ceylon tree flora.) ° ra ' 
(3) The mere marked the climatic periodicity the less the 
interna, forces are obvione and tt/more ^dent a^ th 
relatively equable throughout the 
year, the power of the 
