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 ? 



(6) 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 through mem- 

 branes is known as osmosis. Our experiments have shown 

 that the principles governing the osmotic movement are : 

 (1) the flow of the thinner and lighter liquid toward the 

 denser and heavier takes place more rapidly than in the 

 opposite direction ; (2) the rapidity of the flow depends on 

 the difference in density; (3) solutions of crystallized sub- 

 stances, like sugar and salt, osmose readily ; (4) albuminous 

 substances, such as the white of an egg, osmose so slowly 

 that the cell wall may be regarded as practically imperme- 

 able 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 

 membrane, whether solid, as the outer wall of the cell, or 

 fluid, as the inner wall of living protoplasm. Diffusion may 



