WRIGHT : FOLIAR PERIODICITY 
this is seen in the flora of the Iranativu islands in the Gulf 
of Mannar. When the temperature is high and the air 
saturated with moisture, as in the hilly districts in the south 
of Ceylon, the vegetation iB abundant and succulent types 
frequently occur. Roughly speaking, as one passes from an 
area where the humidity is medium to one where the air is 
very dry, or where it is very moist, the plant adaptations 
against excessive transpiration are on the increase. The 
adaptations are such that the trees transpire partially or 
wholly by means of their stems, and the leaves become 
more or less negligible in the function of transpiration ; in 
other cases the leaves may reduce their stomata in number 
and size and increase the water capacity of the internal 
tissues. In the other class of plants about to be considered 
the adaptations to transpiration are seen in the partial or 
complete defoliation of the trees and the output of new 
leaves at various periods, and in order to understand this 
it is necessary to first discuss the question as to the 
relative amount of water lost by transpiration in temperate 
and tropical zones, a point which has been the subject of 
much experiment. 
Giltay states, according to Schimper, that the daily 
transpiration in plants of Helianthus tuberosus grown at 
Buitenzorg and Holland is approximately the same, viz., 
0*6 gram per hour, though transpiration at midday, at the 
former place, is considerably greater than that in the latter. 
Haberlandt made determinations of the relative amounts of 
moisture lost from the leaves of trees like Albizzia moluccana 
and Theobroma Cacao, at Buitenzorg, and Pyrus communis, 
&c., at Graz. His experiments proved that the transpiration 
in shade, in moist tropical climates, is much weaker than in 
middle Europe. 
Haberlandt’s results have been criticised by Burger stein* 
and others, who point out that, the conclusions can only 
applied to a few plants under the conditions described 
* Rurgersteia, A.; Die Transpiration der Pflanae®; Jena. 1004, p. 161. 
ZJ? 
