IN CEYLON. 
469 
internal forces is obvions on every hand. In East Java and 
in Ceylon the climate is not equable throughout the year, 
and the power of internal and external forces is to be seen 
in various degrees. In the temperate zone, the climatic 
periodicity is more strongly pronounced and the internal 
factors almost obliterated. 
(4) There is evidence to show that a marked climatic 
periodicity in which a drought is involved tends to induce 
a partial deciduous phenomenon in trees which, under a less 
exacting climatic periodicity are evergreen, e.g ., Thespesia 
populnea, Sol., Diospyros ovalifolia, and D. mon tana. The 
same may be said of Tectona grandis in East Java and 
Buitenzorg. 
(5) There is also evidence to prove that a species which is 
deciduous in its natural home where a climatic periodicity 
is pronounced, may, when introduced to other countries, 
retain its periodicity if a climatic periodicity prevails, or it 
may tend to become evergreen if the climate is equable 
throughout the year, e.g,, Poinciana regia at Buitenzorg, 
East Java, and Ceylon, and Schizolobium excelsum in 
Buitenzorg and Ceylon. 
(6) The arborescent flora in a temperate zone is mainly 
deciduous, and it seems possible that those plants the 
periodicities of which were or have been made to coincide 
with the winter months are among the most likely to 
survive. 
In the temperate zones the flora is mainly comprised of 
plants which have survived the exigencies of extremes of 
climate such as the carboniferous rocks and glacial epochs 
indicate, and which are even now annually subjected to the 
frosts of winter and dry heat of summer. On the other 
hand it can be asserted that the plants in the equatorial zones 
are the phylogenetic outcome of forms long existing there, 
since there has been an unbroken condition for the devel¬ 
opment of plants, undisturbed by glacial periods or by 
temperate zone winters. 
8(9)05 (15) 
