Foliar Periodicity of Endemic and 
Indigenous Trees in Ceylon. 
HERBERT WRIGHT. 
(With plates XXV. to XXX.) 
A STUDY of the behaviour of plants in a tropical region 
where the conditions for growth are more favourable 
than in Europe has always attracted the attention of botanists, 
and since 1900 a considerable amount of time has been spent 
in studying the foliar periodicities in plant life with the object 
of tracing out some of the laws which govern these pheno¬ 
mena. There are several problems to consider, such as the 
relationship between the time, manner, and frequency of 
defoliation of trees in the tropics and in middle Europe; 
also how far the phenomena of leaf-fall and foliar renewal, 
in the tropics, are affected by external and internal forces, 
and to distinguish cases in which either or both of these 
factors are of importance. 
The amount of variation to be met with in trees commonly 
deciduous in various parts of Ceylon, the relation of defolia¬ 
tion to transpiration, and the independent effects of heat, 
light, and moisture, are some of the problems which are here 
considered. The following synopsis will indicate the general 
arrangement of the present paper :— 
h —General. 
*2.—Periodicity in Growth. 
Periodicity in temperate and tropical zones. 
Periodicity of vegetation in Ceylon; her¬ 
baceous and shrubby. 
Periodicity of trees in Ceylon. 
Forest types. 
Frequency of foliar activity. 
