THE LEAF 131 
and a certain loss by respiration, but, for the short 
period involved, these will be so small that they may 
be neglected. 
The Stomata provide the outlet for the water of 
transpiration. Place a geranium shoot in a flask of 
water under a bell jar, in such a way that in some 
eases the under and in others the upper = sur- 
faces of the leaves are in contact with the 
class. If this jar be placed in a good light 
and the atmospherie conditions are favourable, it 
will be found that where the under sides of the leaves 
touch the glass great beads of moisture appear, while 
the glass in contact with the upper sides receives only 
a thin film (Fig. 92). It has already been noted that 
most of the stomata are on the under side of the leaf, 
and hence it would appear that the water passes from 
the leaf through these openings. This view is further 
supported by the result of the following experiment. 
Using oil as before to cover the surface of the 
water, in separate flasks stand two shoots of some 
plant in which the stomata are practically all on the 
underside of the leaves, as is the case with the camellia, 
laurel, and karaka. In one shoot, block up the stomata 
by smearing the lower sides of the leaves with vaseline 
(Fig. 89). It will be found that the water falls much 
more rapidly in the flask bearing the shoot in which 
the leaves are not so smeared, again indicating that the 
stomata form the chief avenue of transpiration. In 
this experiment, a good result will not generally be 
obtained till after the shoots have been left standing 
for a few days, since all the plants mentioned are more 
or less drought forms, in which the thickened epidermis 
is specially adapted to check transpiration. 
Perhaps the most satisfactory way of showing that 
the water is given off chiefly from the under sides of 
the leaves is to apply to either surface of a growing 
leaf a piece of filter paper soaked in a solution of 
