126 SOUTH AFRICAN BOTANY 
by a membrane they will diffuse through it, the less 
dense liquid diffusing more quickly than the other. This 
process is known as Osmosis, and can be demonstrated 
by a simple experiment. 
89. Experiment 2.—To show the process of Osmosis. 
Apparatus.—Thistle funnel, piece of bladder, or other 
membrane, sugar, water, red ink, beaker, stand. 
Method.—Tie the membrane tightly over the thistle 
funnel, and fill it with a solution of sugar and water 
coloured with red ink. Fix this to a stand, so that it 
dips into a beaker of pure water, and note the level of 
the solution in the tube of the thistle funnel. Leave for 
fifteen. minutes, or longer. 
Result—The sugar solution rises slowly in the tube 
(an inch or more in an hour), and in a few hours the 
water in the beaker is coloured pink and tastes sweet. 
Deduction.—Both liquids have diffused through the 
membrane, but the pure water has passed into the 
thistle funnel more quickly than the sugar solution has 
passed out (since the level rises), and it can easily be 
shown that the sugar solution is denser than pure water. 
Note.—¥ox the membrane use either a piece of bladder 
which can be obtained from any butcher, or the mem- 
brane of an egg. The latter gives quicker results, and 
can be used with an ordinary piece of glass tubing in- 
stead of a thistle funnel. To obtain it, break the top 
off an egg, empty out the contents, and place the shell 
in dilute hydrochloric acid for twenty-four hours. 
The shell will then all dissolve away, and a tough thin 
membrane will be left. 
90. Osmosis in Roots.—The membrane represents the 
cell-wall of each root-hair, the two liquids represent the 
cell-sap in the root-hair and the water in the soil. But 
