CONTENTS. 



PAGI 



INTRODUCTION . 1 



CHAPTER I. 

 THE POLAR ZONE . 8 



CHAPTER II. 

 THE ARCTIC (AND ANTARCTIC) ZONE 18 



CHAPTER III. 

 THE SUB-ARCTIC (AND SUB-ANTARCTIC) ZONE ... 29 



CHAPTER IV. 

 THE COLDER TEMPERATE ZONE 44 



CHAPTER V. 

 THE WARMER TEMPERATE ZONE ... 93 



