CONTENTS IX 



B. Chemical Properties 94 



C. Physical Properties 95 



VIII. The Tobacco Ringspot Virus 96 



A. Physical Properties 97 



B. Chemical Properties 98 



IX. The Turnip Yellow Mosaic Virus 98 



A. Purification 98 



B. Further Purification 99 



C. Properties of the Preparation 99 



D. The Two Components 101 



E. Amino Acid Composition 105 



F. The Nucleic Acid 106 



X. The Wild Cucumber Mosaic Virus 107 



A. Purification 107 



B. The Two Components 107 



XI. The Tobacco Necrosis Viruses 108 



A. Purification 109 



XII. The Alfalfa Mosaic Virus 110 



XIII. Broad Bean Mottle Virus Ill 



A. Properties Ill 



XIV. The Southern Bean Mosaic Virus 112 



A. Purification 112 



B. Crystallization 112 



C. Physical Properties 113 



D. Chemical Composition 113 



XV. Potato Virus X (Potato Latent Mosaic Virus) 113 



A. Purification 114 



XVI. The Use of Nucleic Acid Analogs in the Control of Plant 



Viruses 115 



A. Azaguanine 117 



References 119 



III. Variation and its Chemical Correlates by C. A. Knight 127 



I. Introduction 127 



A. Historical 127 



B. Terminology 128 



C. Frequency of Mutation 129 



J). Significance of Mutation 130 



II. Plant Virus Strains 130 



A. Characteristics of Strains 130 



B. Methods for Securing Strains 131 



C. Criteria of Strain Relationship 1S3 



D. Evaluation of Criteria of Strain Relationship 138 



