54 PRACTICAL COURSE IN BOTANY 
of water in the tube? What has become of it? How did it get out? 
Taste it to see if any of the salt water has got in. Which is the heavier, 
salt water, or fresh? (If you do not know, weigh an equal quantity of 
each.) In which direction did the principal flow take place; from the 
heavier to the lighter, or from the lighter to the heavier liquid ? 
(b) Put a sugar or salt solution in the tube, and clear, fresh water in 
the glass, marking the height in each as before. Does the liquid rise or 
fall in the tube? Does any of it escape into the water of the glass, and if 
so, is it more or less than before? Which now contains the denser fluid, 
the tube or the glass? What principle governs the course of the liquid? 
Try the same experiment with (c), the same liquid in both vessels, and 
notice whether there is a greater flow in one direction than the other, as 
indicated by a comparison with the marks on the outside. (d) Put in 
the tube some of the white of a raw egg, insert in a glass.of pure water, and 
note the effect. (e) Reverse, with water in the tube and white of egg 
in the glass. Does the water rise in the tube as before? Test the contents 
for proteins; has any of the albumin passed through the membrane into 
the tube? 
Experiment 40. To TEST THE BEHAVIOR OF LIVING AND DEAD CELLS. — 
Slice a fresh piece of red beet into a vessel of water and of a boiled one into 
another vessel of the same liquid at the same temperature. What differ- 
ence do you notice? Can you think of any reason why the boiled one gives 
up its juices and the other one does not? 
56. Osmosis. — The passage of liquids or of solids in so- 
lution through membranes is known as osmosis. Our experi- 
ments have shown that the principles governing the osmotic 
movement are: (1) the passage of water from the thinner 
liquid toward the denser takes place more rapidly than in 
the opposite direction; (2) the rapidity of the transfer de- 
pends on the difference in density; (3) crystallizable sub- 
stances in solution, like sugar and salt, osmose readily; 
(4) albuminous or gelatinous substances, such as the white 
of an egg, osmose so slowly that the cell wall may be regarded 
as practically impermeable to them. 
57. Osmosis a form of diffusion. — Osmosis is related to 
diffusion as a part to the whole. In other words, it is a name 
given to the process when it takes place through a mem- 
brane, whether solid, as the outer wall of the cell, or semi- 
fluid, as the inner wall of living protoplasm. Diffusion may 
