1 Polyhedral Plant Viruses with Monopartite RNA Genomes: Introduction and Summary of Important Properties.- 2 Tombusviruses.- I. Introduction.- II. Diseases, Host Ranges, and Geographical Distribution.- A. General Features.- B. Diseases.- III. Transmission, Ecology, and Control.- A. Transmission.- B. Ecology.- C. Control.- IV. Purification.- V. Properties of Virus Particles.- A. Particle Morphology.- B. Sedimentation.- C. Electrophoretic Properties.- D. Coat Protein Subunits.- E. Structure of Virus Particles.- VI. Serology and Immunochemistry.- A. General Features.- B. Serology in Virus Identification.- C. Serology in Virus Classification.- D. Immunochemical Studies.- VII. Genome Properties and Replication.- A. Structure of Genomic RNA.- B. Expression of the Genome.- C. Viral Replication.- VIII. Relations with Cells and Tissues.- A. General Cytology of Infected Cells.- B. Appearance and Intracellular Distribution of Virus Particles.- C. Inclusion Bodies.- IX. Satellites.- X. Recent Developments.- References.- 3 Carnation Mottle Virus and Viruses with Similar Properties.- I. Introduction.- II. Geographical Distribution, Host Range, and Transmission.- A. Diseases of Ornamental Crops.- B. Diseases of Cucurbits.- C. Diseases of Legumes.- D. Viruses of Other Hosts.- III. Purification.- IV. Properties of the Virus Particles.- A. Particle Morphology.- B. Physical and Chemical Properties.- C. Virus Particle Structure.- V. Serological Properties.- VI. Genome Properties and Replication.- A. Genome Structure.- B. Regulation and Expression of the Genome.- C. Viral Replication.- VII. Cytopathology.- VIII. Satellites.- IX. Conclusions.- X. Recent Developments.- References.- 4 The Sobemovirus Group.- I. Introduction.- II. The Viruses and Diseases.- A. Southern Bean Mosaic Virus.- B. Blueberry Shoestring Virus.- C. Cocksfoot Mottle Virus.- D. Lucerne Transient Streak Virus.- E. Rice Yellow Mottle Virus.- F. Solanum Nodiflorum Mottle Virus.- G. Sowbane Mosaic Virus.- H. SubterraneanlS^