IN CEYLON. 
447 
Haberlandt, and that it would not be fair to assume that the 
loss by transpiration would be so small from forest and 
other trees exposed to tropical conditions. 
Wiesner* worked with herbaceous plants such as Coleus, 
Adiantum, Jatropa, and Mimosa pudica and proved that these 
plants, at Buitenzorg, lost very large quantities of water 
during hot cloudless days. 
Wiesner also proved that in the temperate zones the 
early deciduous species may lose a greater quantity of water 
than those which drop their leaves later in the year, and in 
some cases even more than those which are evergreen. 
Transpiration in Ceylon . 
Holtermann, who worked in various parts of Ceylon, has 
published some interesting results bearing on this subject. 
Describing the humidity of the air at Peradeniya, he points 
out that on ordinary days with a clear sky, in the dry season, 
evaporation commences after sunrise and remains feeble up 
to 10 A.M., but from this time it increases until between 
twelve and three it reaches its maximum, and then decreases 
until sunset, and subsequently dew is formed. Transpira¬ 
tion stops nearly or completely after sunset, when saturation 
point is being approached. The stomata are usually closed 
during the night. 
At Peradeniya, from January to March there is a dry wind, 
and during this period transpiration is greater, and may 
even continue all through the night. The evaporation on 
moist days, when the air is saturated, is very slight or scarcely 
perceptible. In order to emphasize the great difference 
between the transpiration during hot dry and wet days he 
states that Asplénium Nidus during misty days lost from 
0 00 to 0*21 gram of water per day, but on a sunny day it 
transpired as much as 3*50 grams. 
Holtermann worked with various plants. Cymbidium 
bicolor—a common epiphytic orchid—was selected among 
* Wiesner, Julius ; Über Laubfall infolge Sinkens des absoluten Licht- 
genusses (Sommerlaubfall) ; Botan. Gesel., Berlin, 1804. 
