This is the opening volume in a revised series which will collectively form the second edition of the Anatomy of the Dicotyledons, originally published in 1950. Incorporating years of advances in the field, this new edition necessarily provides a more extensive presentation. Volumes 1 and 2 introduce the general principles and types of data on which the systematic anatomy of the Dicotyledons is based, and show how the discovery and organization of histological characters of vegetative organs can serve as an important element in the general taxonomic classification. The work is the result of support and contributions from botanists in both the United Kingdom and the United States. In subsequent volumes, the histological characters of the individual families will be described in the taxonomic sequence of Takhtajan's system. The first two volumes, however, serve as a textbook of systematic anatomy. No other comprehensive work on this topic exits at present. Volume 1 begins with a historical introduction, then goes on to deal with the leaf and with herbaceous stems as well as with twigs of woody plants. It also includes lists of families in which certain diagnostic features occur, along with an extensive bibliography. Secondary xylem is treated mainly in Volume 2.