Vlii CONTENTS 



CHAPTER IV 



THE PECTIC SUBSTANCES 



PAGES 



Occurrence and properties of pectin and pectase The action of 

 pectase Preparation of pectin Source of pectase Electrical 

 conductivity of coagulated pectin solutions The action of 

 pectase studied by the viscosimeter The influence of ions 

 upon the maximum viscosity of the solution Discussion of the 

 form of the viscosity curves Gelatinization of pectin by 

 alkalies 63 74 



CHAPTER V 

 OSMOTIC PRESSURE IN PLANTS 



Quantitative laws of osmotic pressure The nature of osmosis 

 The nature of semi-permeable membranes ... 75 83 



CHAPTER VI 



THE OSMOTIC EQUILIBRIUM BETWEEN THE CELL AND ITS 

 SURROUNDINGS 



Naked and walled cells Cryoscopy of sap The relationship of 

 the yeast cell to its medium (a) Cryoscopic researches 

 (b) Researches by the method of plasmolysis Comparison of 

 the cryoscopic and plasmolytic methods of measuring osmotic 

 pressures of plant cells - - 84 95 



CHAPTER VII 



THE PERMEABILITY OF PROTOPLASM 



The yeast cell The secretory activity of Colocasia leaves and of 

 the pitcher of Nepenthes The penetration of salts into leaves 

 Overton's theory of the lipoid surface film Surface tension of 

 protoplasm Differential permeability False plasmolysis The 

 permeability ,of protoplasm to salts and ions Precautions 

 necessary in plasmolytic investigations Rate of penetration of 

 salts and ions Criteria of penetration of salts and ions The 

 electrical conductivity of living cells Variations in the per- 

 meability of the living cell; influence of salts and anaesthetics 

 The measurement of the antagonism of ions The effect of 

 alterations in temperature upon permeability The effect of 

 variations in the intensity of illumination upon permeability 

 The constitution of the protoplasmic surface - - - 96 136 



