The new fourth edition has been thoroughly revised and updated to reflect the many advances in science and technology, including the five accepted sequential stages of micropropagation. Ten new plants have been added. This in turn has greatly expanded the already extensive bibliography. Among the new topics that have been introduced or expanded on are embryo culture for breeding, somaclonal variation, anther culture, somatic embryogenesis, cryopreservation, and genetic engineering. More ornamental plant examples are given and many new illustrations provided, including a chronology of discoveries in micropropagation.