
96 THE WORK OF PLANTS 
Further, we cannot see any sign of water until we 
see it accumulating on the jar, so that it must pass off 
from the leaves in a very light form, so light that it 
can float in the air like dust without being visible. 
When water is in this form in the air we call it vapour. 
The water passes off from the leaves in the form of 
water vapour. 
Loss of water from living plants. In the above 
experiment the leaves were removed from the plant. 
It is not certain from this experiment whether the 
water passes off from the surfaces of the leaf or from 
the broken or cut ends of the petioles. 
We are going to test the living plant 
ina similar way. To do this, place a 
potted plant under a tall bell jar, or 
invert a glass jar over the plant, alter 
having covered the pot and soil with 
a flexible oilcloth or sheet rubber, or 
several layers of oiled paper. Tie the 
paper close around the stem of the 
plant to prevent the evaporation of 
water from the soil or pot. During 
Fic. 132. Water isgiven Several hours the moisture film can 
off by the leaves when 
attached to the living be seen forming on the inside of the 
ae glass vessel. Gradually it accumulates 
until numerous drops are formed, some of which in 
time may trickle down the side of the jar. The 

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