A Field Guide to the Birds, the first book in the Peterson Field Guide Series, was published in 1934 and the principle on which it was founded--a schematic approach pointing out the visual or field differences between species--proved a sound one. Checklist or phylogenetic order was often subordinated to an artificial but more practical arrangement of the figures on the plates. For example, the chimney swift was placed with the swallows and the Philadelphia vireo and ruby-crowned kinglet were compared with the confusing fall warblers.

It was inevitable that a field guide to trees, shrubs, and woody vines should follow. In fact, as far back as 1941 I had planned to do such a book and had actually started on it when I learned that George Petrides was deep in the identical project. Upon examining his work I concluded that his version adhered to the basic principles of the Field Guide system even more than mine, so I turned to other projects, offering him bits of supplementary material-tree silhouettes, drawings of fruits and flowers, etc.--that would have gone into my own book. He had based his approach mostly on leaf, twig, and bud characters.

Dr. Petrides, a veteran field naturalist with a record of teaching and research, first in the National Park service and U.S. Wildlife Service and now at Michigan State University, had long felt the need of an approach to plant recognition that his students in ecology and game management would understand. It is well enough to be tutored in basic plant taxonomy, but more often than not the student even after considerable training is still confused when confronted by many problems of identification.

This Field Guide in a sense is a pictorial key using obvious similarities and differences of form and structure by which the beginner can quickly run down his tree, shrub, or vine. True, some botanists may raise their eyebrows because the plants are not in the traditional order of their relationships, but there are many formal botanies so arranged; it would have been pointless to produce another. This guide is a shortcut. Actually the student will learn the relationships too (even if indirectly), for a key in the appendixes makes these quite clear.

To Devereux Butcher I express thanks for his offer of the use of his photographs of trees, several of which were used as reference material in the silhouette section. I only wish that shortage of space had not prohibited a similar section of drawings of the bark of trees. Had this been included, some of the keys would have had to go. These, particularly the winter keys, were deemed indispensable to the usefulness of the book.

This, the first extensive revision in fourteen years, brings numerous refinements to a Field Guide that has already been used for more than 250,000 students, botanists, and amateur naturalists. The plates have been reorganized so as to bear a more convenient relation to the updated text, facilitating quick reference.

In the ecology-oriented years ahead, use this handy book to inform yourself about the green mantle of plants that clothe our "small blue planet," the only home we've got.