HOW THE ROOT LIFTS WATER 9] 
membrane, after soaking it to make it pliant. Pour 
out from the small end enough of the solution so that it 
will stand but a short distance above the bulb 
in the narrow part of the tube. Invert this 
in a bottle partly filled with water, pass a 
perforated cork down the tube and into the 
mouth of the bottle to hold the tube mm posi- 

Fic. 127. A 
“‘ thistle ’’ 
tube. 
tion, and bring the tube 
so that the sugar solution 
in the tube is at the same 
level as the water in the 
bottle. Allow this to rest 
for several hours. 
If the experiment has 
been set up properly, the 
sugar solution now stands 
higher in the tube than 
the level of the water. 
Because the water in the 
tube has sugar dissolved in it, it 1s 
a stronger solution; that is, of a 
stronger concentration than the 
water in the bottle. In such cases, 
where the two liquids are separated 
by a membrane, more water always goes through into 

Fic. 128. Apparatus with 
thistle tube, bladder mem- 
brane, and sugar solution 
to imitate root pressure. 
tie the open end, and place where it will dry. From these dried bladders 
a membrane can be cut whenever wanted, Soak in water before using. 
