
92 THE WORK OF PLANTS. 
the stronger solution. The bulk of the sugar solution is 
thus increased, and it is forced higher up in the tube. 
The root acts much in the same way, except that 
each of the tiny root-hair cells and the tiny cells of the 
root act as the thistle tube and sugar solutions do, or 
as the make-believe cell did. ‘The sap in the cells is a 
solution of certain sugars and salts. The lite substance 
(protoplasm) in each cell lines the cell wall and acts 
like the bladder membrane. ‘The 
water in the soil is outside the 
roots, but comes in touch with 
the life membrane because it filters 
easily through the cell walls. So 
all the tiny cells work together, 
and the result of their combined 
work is like that of the thistle- 
tube experiment. | 
A potato tube may be used to 
represent the work of a single root — 
hair, or of the root. Cut out a 
cylindrical piece from a_ potato 


pee tic tuber. Bore a hole nearly through 
Fie@.129. Th t ° . 
ee. toning. a tube: closed, at..ene 
leaf of lant tak ° ; 
end, Place in the hottom:of this 
brane. ; 
2 tube a quantity of sugar and rest 
the tube in a shallow vessel of water. Observe how 
the sugar becomes wet from the water which is drawn 
