CONTENTS 



CHAPTER I 



PA<5B 



INTRODUCTION 1-4 



What Is Agriculture, p. 1; Divisions of Agriculture, p. 2; Forces 



Controlling Plant and Animal Growth, p. 2; Heredity, p. 2; 



Environment, ' p. 3. 



Questions 3 



Collateral Reading 4 



CHAPTER II 



THE IMPROVEMENT OF PLANTS AND ANIMALS 5-35 



Variation in Plants and Animals 5 



Law of Variation, p. 5; Similar Produces Similar, p. 6. 



Natural Selection 7 



Sports and Mutations, p. 8; The Development of Weeds 

 by Natural Selection, p. 8; De Candolle's Law, p. 9. 



Artificial Selection 10 



Reproduction in Plants 11 



Seed-Producing Organs of Plants, p. 11; Sexual and Asexual 

 Reproduction, p. 12; Artificial Crossing, p. 13. 



Some Principles of Heredity 13 



Problems of Heredity, p. 13; Mendel's Law, p. 14; Appli- 

 cations of Mendel's Law, p. 19. 



Steps in Breeding 21 



Increasing Variation, p. 21; Selection, p. 21; Testing Heredi- 

 tary Power, p. 22. 



Improving Some Farm Crops 23 



Plant-Breeding vs. Animal-Breeding, p. 23; Comparative 

 Improvement of Different Crops, p. 23; Sugar Beet, p. 24; 

 Corn, p. 25; Cotton, p. 29; Other Cross-Fertilized Plants, 



(xi) 



