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 ? 



(&) 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 



