^ CONTENTS 



t 



ACKNOWLEDGMENTS AND FOREWORD 5 



Introduction 7 



A Genetic Classification of Vegetation 8 



The Factors Controlling Distribution 8 



The Nature of Crop Ecology 11 



PART ONE 



PLANT SUCCESSIONS 13 



The Orientation of the Field op Ecology 15 



autecology 15 



Synecology 16 



The Factors in Successions. 1. Climatic 17 



The Relation of Climate to Plant Distribution 18 



The Source of Land Evaporation 20 



Movement of Air Currents 22 



The Soil Factors 25 



The Biotic Factors 27 



Summary of Climatic, Edafhic, and Biotic Factors 30 



Examples of Succession 31 



PART TWO 



FACTORS INFLUENCING CROP DISTRIBUTION IN THE U. S 33 



PART THREE 



THE CROP REGIONS OF OHIO AND THEIR SIGNIFICANCE 43 



Topography and Drainage 43 



The Soils 46 



The Climatic Conditions 48 



The Vegetation Centers 54 



The Crop Centers of Ohio 56 



SUMMARY AND CONCLUSIONS 69 



LITERATURE CITED 73 



i-07c>^3 



