ABSORPTIO.V. DIFFUSION, OSMOSE. 



17 



33. Let us no«- remove some of the slii es 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 

 inter from the tormer 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 becomes 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- Fig- 25. 



Before treatment \\-ith salt .\fter treatment with salt Later stage ol the same, 



solution. solution. 



Figs. 23-25. — Cells from beet treated ^ith 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 obser^'ed in 

 the case of spirog^'ra. "^ Now treating the section with water and removing 

 the salt solution, the diftusion 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 difterentiate 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. 



