
88 THE WORK OF PLANTS 
minute vessels or tubes which are continuous with 
similar tubes in the stem. The contimued pressure 

Fig. 124. Cutting off stem of 
balsam plant. 
which is formed in the roots lifts 
the water up and forces it out 
through the cut end of the stem. 
(The bleeding of cut stems in 
winter or early spring is due to 
changes in the expansion of the 
air, because of the great difter- 
ences in temperature. ) 
Root PRESSURE IN A GARDEN 
BALSAM 
The materials necessary for the 
study. Select a vigorously grow- 
ing potted garden-balsam plant. 
If this is not at hand, use a coleus 
plant, geranium, or other plant. 
Select a piece of glass tubing 
several feet long and about the 
same diameter as that of the stem 
of the plant to be used. Next 
prepare a short piece of rubber 
tubing which will slip over the 
end of the glass tube. ‘Then 
have ready some wrapping cord, 
a small quantity of water; a tall stake, and a sharp knife. 
