CHEMICAL PHENOMENA IN LIFE 



regulating the osmotic change of substances 

 with the outer world. While the cellulose mem- 

 brane of the cell is only a dead cover of the living 

 contents, the living plasmatic membrane is 

 variable in its condition and is quite different 

 when in its normal living state and when dead. 

 If slices of beet-root are dipped in water, after 

 having the remainder of the cells which were cut 

 through properly washed off, one may keep them 

 in water for any length of time without losing 

 even a trace of the red colouring matter in the 

 living cells. But if chloroform is added to the 

 water and the cells are killed by the narcotic 

 agent, streams of red colour go out from the 

 tissue. The dead protoplasmatic membrane is no 

 -longer able to retain the contents of the cell. 



In the living cell the decision to take up dis- 

 solved substances from the liquid outside the cell 

 lies with the protoplasmatic membrane. Even 

 the well-known fact that the chemical constitution 

 of plants is quite different from that of the soil in 

 - which they are growing, proves the elective in- 

 fluence of the protoplasmatic membrane in 

 endosmosis. This elective influence is much 

 better shown by the phenomenon of Plasmolysis. 



We owe to Hugo de Vries, of Amsterdam, the 

 excellent method here described. It is best to 

 choose cells with red-coloured cell sap for the 

 experiments. Such cells are found on the under 

 surface of many leaves. Corollary petals may also 



36 



