452 
WRIGHT : FOLIAR PERIODICITY 
If the reduction in transpiration is really of vital import¬ 
ance or even an appreciable advantage to the plant, one 
would expect to find some semblance to order and regu¬ 
larity, particularly in the period during which the plants 
are leafless and the time of production of young tender 
foliage. 
Holtermann proved that transpiration was greater from 
young leaves than from old ones, and greater during the 
hot dry period at Peradeniya than during other parts of the 
year. Yet there are many trees, e.g ., Albizzia procera, with 
tender thin foliage which retain all their leaves during the 
period when transpiration is at the maximum ; and, on the 
other hand, trees such as species of Ficus,with tough leathery 
leaves coated with a thick cuticle and therefore probably 
losing less by transpiration, become leafless. If, however, 
species such as Bombax malabaricum or Cratæva Roxburghii 
be considered, the reduction in transpiration will be found 
to be very great. The Bombax trees remain leafless for 32 to 
96 days during our hottest and driest period, and usually 
produce new leaf at the end of the drought. One tree of 
Cratæva Roxburghii has been observed to be leafless for 
31 to 76 days each year, and this specimen never regains full 
foliage until March or April. But when species such as 
Phyllanthus indicus, Careya arborea, Ficus Tsjakela, Ster- 
culia Balanghas, Terminalia belerica, Chickrassia tabularis, 
and many others are studied it is seen that though they 
become leafless during the hot months for one or two 
days or weeks, they always produce their complete 
outfit of new' tender foliage while the hot dry season is 
prevailing. 
For these reasons one must assume that checking trans¬ 
piration is only a consideration to certain species, and that 
others may, by passing through their foliar stages like those 
last mentioned, actually lead to an increase in transpiration 
at a time when the minimum quantity of water is available 
in the soil . 
