92 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



The 25 per cent, solution is 2-77 normal, and has a cal- 

 culated osmotic pressure of about 70 atmospheres. Owing 

 to the association of the glycerol molecules, the osmotic 



10 



15 20 25 



%Glycerol ' 



FIG. 5. 



30' 



pressure may, however, be considerably less in reality. 

 Inspection -of the figure makes it clear that, whilst some 



FIG. 6. 



of the cells, the oldest ones, had comparatively low osmotic 

 pressures, others could withstand very great external 

 pressures without plasmolysis. The values obtained by 



