Martin : Effect of concentrated solutions 417 



did not check cyclosis, and after two hours slow streaming was 



o 



still visible. 



Glycerine, {a) Isotonic concentration. — nj^ glycerine was the 

 concentration required to produce plasmolysis in Philotria. 



(b) Increase in concentration of cell-sap, — In order to deter- 

 mine the increase in the concentration (for potassium nitrate) due 

 to the action of glycerine, a (cw leaves were placed in Van Tieg- 

 hem cells filled with ///3 glycerine. After a lapse of some hours 

 these were tested wath solutions of potassium nitrate. 



(i) ;;/4 potassium nitrate, the isotonic concentration, did not 

 plasmolyze cells o{ Philotria, which had been in nji glycer- 

 ine about five hours. 



(2) It required ///j potassium nitrate to plasmoly;^e cells which 

 had been in nj^^ glycerine five hours. The action was very 

 uneven, showing complete plasmolysis in some cells and 

 none in others, especially the apical cells. This was no 

 doubt due to the greater permeabih'ty of the apical cells, 

 which had therefore absorbed more glycerine. 



(3) From 2;//5 to 97^/20 potassium nitrate was required to 

 plasmolyze cells which had been in nji glycerine twenty- 

 four hours. 



The above experiments show that not only is the concentration 

 of the cell-sap increased by the penetration of glycerine, but that 

 the longer the action is allowed to go on the stronger the osmotic 

 pressure of the cell-sap becomes. 



Uj-ea. (a) Isotonic concentration. — nj^ urea usually failed to 

 plasmolyze cells of Philotria^ but ///3 urea would plasmolyze nearly 

 every cell. 



{b) Increase in concentration of ccllsap. — Leaves were put in 

 solutions in Van Tieghem cells, as in the above experiments with 

 glycerine. Since nj^ urea sometimes produced plasmolysis, tests 

 were made for increase in concentration of sap with both w/4 and 

 ^/3 urea. 



(i) nil potassium nitrate produced only incipient plasmolysis 

 in a {^\\r cells of leaves which had been m nj^. urea about. 



twenty-four hours. 

 (2) 2«/5 potassium nitrate was required to produce plasmoly- 

 sis in such cells. The action was slow and gradual, vary- 

 ing from incipient to strong. 



