CONTENTS xiii 



CHAPTER VI 



The Income, Movements, and Outgo op Materials in 

 Plants 



PAGE 



Cells are Bags of Water 52 



Permeability 52 



Osmotic Pressure 53 



Living Cells are Osmotic Systems 53 



The Structure of Roots 53 



Mechanical Results of Root Structure 55 



Movement of Water and Dissolved Substances 56 



The Structure of Stems 56 



The Ascent of Sap 57 



The Structure of Leaves 58 



Leaves as Absorbing Organs 59 



Leaves as Organs of Gas Exchange 60 



Evaporation 60 



Roots as Excreting Organs 61 



Secretion and Excretion 61 



Guttation and Bleeding 61 



CHAPTER VII 



The Storage and Digestion of Foods in Plants 



Storage .' 63 



The Common Places of Storage 63 



The Places of More Permanent Storage 63 



Starch 64 



Other Stored Foods 64 



Means of Moving Manufactured Foods 65 



The Paths of Movement 65 



Digestion 66 



The Means of Digestion 66 



Catalyzers 66 



Enzyms 67 



Classification of Enzyms 67 



Germination and Spring Growth 69 



Section 3. The Maintenance of Life 



CHAPTER VIII 

 The Utilization of Food 



Reasons Why Living Things Require Food '. . Ts 



Metabolism in General 74 



Basic Metabolism 74 



Growth Metabolism 75 



The Manufacture of Material 75 



The Metabolism of Active Function 75 



Nervous Activity 76 



