ABSORPTION, DIFFUSION, OSMOSE. 



17 



33. Let us now remove some of the slices of the beet from 

 the sugar and salt solutions, wash them with water and then 

 immerse them in fresh water. In the course of thirty minutes 

 to one hour, if we examine them again, we find that they have 

 regained, partly or completely, their rigidity. Here again we 

 infer from the former experiment with spirogyra that the sub- 

 stances in the cell-sap now draw water inward ; that is, the 

 diffusion current is inward through the cell walls and the proto- 

 plasmic membrane, and the tissue becoines turgid again. 



34. Osmose in the cells of the beet. — We should now make a section of the 

 fresh tissue of a red colored beet for examination with the microscope, and 

 treat this section with the salt solution. Here we can see that the effect of the 

 salt solution is to draw water out of the cell, so that the protoplasmic mem- 



Fig. 23. Fig. 24. 



Before treatment with salt After treatment with salt 



solution. solution. 



Fig. 25. 

 Later stage of the same. 



Figs. 23-25. — Cells from beet treated with salt solution to show osmosis and movement of 

 the protoplasmic membrane. 



brane can be seen to move inward from the cell wall just as was observed in 



the case of spirogyra.* Now treating the section with water and removing 



the salt solution, the diffusion current is in the opposite direction, that is in- 



* We should note that the coloring matter of the beet resides in the cell- 

 sap. It is in these colored cells that we can best see the movement take 

 place, since the red color serves to differentiate well the moving mass from the 

 cell wall. The protoplasmic membrane at several points usually clings tena- 

 ciously so that at several places the membrane is arched strongly away from 

 the cell wall as shown in fig. 24. While water is removed from the cell-sap, 

 we note that the coloring matter does not escape through the protoplasmic 

 membrane. 



