Although only about 3 years have passed since the preparation of the original manuscript of this book for the Russian edition, the number of successful experiments on somatic hybridization of higher plants has doubled. Although the main inferences of the first edition still remain in force, most of them have received conclusive experimental support and, moreover, some new con­ clusions have been drawn. It can be expected that these inferences and conclusions will constitute a more or less durable foundation for somatic cell genetics of higher plants. We thus hope this book will also remain useful over the next years, in spite of the rapid progress of experiments and the increase in the number of scientific reports in this field. Though it might appear strange to an uninvolved observer, the principal progress in hybridization of somatic cells of higher plants has been due to plant physiologists (who entered the field by elaborating methods and techniques for plant cell and, later, for isolated protoplast culture) rather than plant geneticists. However, further qualitative improvement in this field is inconceivable without the instillation of genetic ideology and the strict logic of genetic experiments. The main purpose ofthis book is the attempt to organize the available experimental data in terms and cate­ gories of genetic analysis. For this reason, this book lays no claim on being a comprehensive treatise on somatic hybridization.