OSMOTIC PROPERTIES OF THE CELL. 



39 



Reinke has ascertained, firstly, that the amount of evaporation 

 from an organised structure depends upon the degree of its 

 saturation ; it is greatest when the body is fully saturated : 

 secondly, that the pressure which is necessary to force water 

 out of an organised body is at its minimum when the body is 

 at its maximum degree of saturation or imbibition. 



III. The Osmotic Properties of the Cell. 



It has been already pointed out in the case of Yeast, that 

 the cell is capable of absorbing water containing various sub- 

 stances in solution, and, now that we have learned something 

 as to the structure of the cell, we are in a position to study 

 this process in detail. If a section of a succulent stem, 

 mounted in distilled water, be examined under the microscope, 

 it will be seen that the parenchymatous cells are fully ex- 

 panded, that they evidently contain as much water as they 



FIG. 9 (after de Vries). Young parenchymatous cell from the peduncle of Cepha- 

 laria leucantha: i, Turgid cell ; 2, the same cell in 4 per cent, nitre solution ; 

 3, in 6 per cent, solution; 4, in 10 per cent, solution, shewing complete 

 plasmolysis : h, cell-wall ; p, primordial utricle ; k, nucleus ; c , chlorophyll- 

 corpuscles ; s, cell- sap ; e, nitre solution which has entered the cell. 



possibly can. Cells in this condition are said to be turgid. 

 If now a 4 per cent, solution of nitre be substituted for the 

 distilled water, it will be observed that the cells become 



