BOTANICAL GAZETTE 



[SEPTEMBER 



by means of a hand press giving about 300 kgm. per sq. cm., the 

 tissue having been coarsely cut up with scissors and wrapped in a 

 single layer of art canvas. The freezing point was determined with 

 the Beckman apparatus, following the directions given by Ham- 

 burger (10). Both osmotic pressure and permeability were 

 investigated by the plasmolytic method. Plasmolysis was ob- 

 served in the cortical cells just underlying the epidermis at the 

 base of the second leaf scale (that is, second from cotyledons). 

 Plasmolytic agents employed were sucrose, glucose, KN0 3 , and 

 glycerine. A solution was considered isotonic with the cell sap 

 if it just caused plasmolysis after 30 minutes. The temperature 

 was 20-24 C. 



TABLE VIII 

 Osmotic pressure by freezing point 



In table VIII are the results by the freezing point method. It 

 is evident that the juice of the treated tissue has a higher osmotic 

 pressure than that of the control, a difference of about two 

 atmospheres. 



Similarly, table IX gives the results by the plasmolytic method. 

 The figures show that the same relative difference of about two 

 atmospheres exists between the treated and untreated tissues, 

 although the pressures themselves are somewhat higher. Richter 

 (31) and others have assumed a rise of osmotic pressure in tissues 

 under the influence of anaesthetics. This assumption is based 

 upon the fact that sugars and other osmoticaHy active substances 

 were known to increase. However, no 'previous measurements 



