TABLE OF CONTENTS 



CHAPTER ^^°^ 



I. INTRODUCTION 1 



A. Outline of the Book 1 



B. Definitions 3 



C. Previous Reviews of the Field 4 



II. DEVELOPMENT OF THE HORMONE CONCEPT . . 6 



A. Correlation and Formative Substances 6 



B. Tropisms 9 



C. Birth of the Growth Hormone Concept 11 



D. Isolation of the Growth Hormone 13 



E. Other Hormones in Higher Plants 17 



III. THE TECHNIQUE OF AUXIN DETERMINATIONS . 21 



A. Morphology of the Avena Seedling 21 



B. Evolution of the Avena Test Method 24 



C. The Avena ISIethod in Its Present Form 27 



1. Dark Room and Equipment 27 



2. Preparation of Test Plants 28 



3. Preparation of the Agar 34 



4. Technical Modifications 36 



5. Evaluation of Results 38 



6. Positive Curvatures 42 



7. The Maximum Angle 45 



8. Variability of the Test 49 



D. Other Methods of Auxin Determination 51 



1. Straight Growth 51 



2. The Pea Test 54 



3. Epinastic Responses 56 



4. Other Methods 56 



IV. FORMATION AND OCCURRENCE OF AUXINS . . 57 



A. The Formation of Auxin in the Plant 57 



B. The Auxin Precursor 64 



C. Distribution of Auxin in the Plant 67 



D. Auxin in Animal Material 70 



E. Production of Auxin by Microorganisms 71 



V. THE RELATION BETWEEN AUXIN AND GROWTH . 73 



A. Auxin and the Growth of Coleoptiles 73 



B. The Role of the Food Factor 79 



C. The Limitation of Size in the Plant 80 



D. Applications of the Two-Factor Scheme 81 



E. Auxin Inactivation and Dwarf Growth 86 



F. Radiation and Its Effects on Auxin 88 



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