102 THE WORK OF PLANTS 
This work 1s done by the timy cells of the leaf. 
The leaf, then, can help lift water in the plant. This 
can be well shown by the experiment in Fig. 137. 
A leafy shoot of coleus, geranium, or other plant is 
cut, and connected by a short piece of rubber tubing 
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Fig. 137. Showing that the leaf can 
raise water in the stem as it is given 
off at the surface. 
to one end of a bent, or U, 
tube which has been filled 
with water so that the end 
of the cut shoot is in con- 
tact with the water. The 
rubber tube must be tied 
tightly both to the shoot 
and to the glass tube, so 
that air cannot get in. As 
the water transpires from 
the leaf it is gradually 
drawn from the tube so 
that it lowers in the other 
arm of the tube. When the 
water is nearly all out of 
this arm, mercury may be 
poured in, and after a time 
the mercury will be lifted 
higher in the arm of the tube which is connected with 
"thecplant than in°the other. Mercury is a great deal 
heavier than water, so the leaves can do some pretty 
hard work in lifting. 
