466 WRIGHT : FOLIAR PERIODICITY 
be correlated with climatic differences, and may in a great 
measure be due to internal requirements only. 
An interesting point was also observed in connection 
with cuttings of Erythrina indica. Several cuttings in 
October, 1903, about 4 feet long, were stripped of all leaves 
and put into ordinary soil for cultivation as a green manure. 
They soon burst into leaf, many of them continued without 
a break in full vigour, but a very large number dropped all 
their leaves and passed through the leafless period during 
February and March. Many regained their foliage. Thismay 
indicate that the fall of leaf from the trees is an inherent 
character and must be of a curious nature, since it is not 
much changed by propagation from a cutting, the cutting 
behaving like a tree though it is not a year old. 
\ 
External Forces . 
Our knowledge of the different behaviour of the same 
species at Buitenzorg and East Java, of the many well-known 
instances of acclimatization in various parts of the world, and 
the behaviour of introduced species in Ceylon, convince us 
that climate exerts a recognizable influence on the foliar and 
floral periodicities of tropical plants. 
Previous observations have shown that certain species 
are not affected by the climatic periodicity, and those 
cases which indicate that the time of foliar activity is 
influenced by the climate can now be dealt with. The most 
striking fact which impresses one with the power of the 
dry period is that more than half of the deciduous endemic 
and indigenous species pass through their leafless phase 
from January to March. These species show a response to 
climate, in so far that in districts similar to Peradeniya they 
drop all their old leaves and remain leafless during a part 
of the hottest and driest season. During this period the 
leafless twigs of Bombax malabaricum, Eriodendron anfrac- 
tuosum, Spondias mangifera, Careya arboreya, Gmelina 
arborea, Ficus Arnottiana, Berrya Ammonilla, Terminalia 
