Preface: With the large number of books now available featureing North American trees, the launching of another on this subject merits perhaps some explanation. Most present tree manuals fall into one of two classes: (1) encyclopedic, such as Sargent's monumental "Silva of North America," later condensed into one volume, which has been adapted by nearly every writer of tree books since it first appeared; and (2) local, as exemplified by the many excellent state and regional manuals. Nearly all these publications have been written from the botanical or taxonomic standpoint and in general treat each species in the same detail. It is obviously impossible for a beginning student in forestry to gain an adequate knowledge of more than a few of the thousand tree species native to this continent. Rather, it is desirable only to cover as many groups (genera) as possible, and to illustrate these with the species of greatest importance to forestry.^ Such a treatment, accompanied by adequate photographic halftones, has not been available to date, and the authors hope that the present book will fill this need. The native coniferous genera have all been included because of their relative importance, and fewer numbers; but several families, and many genera species of the broadleaved trees have been omitted. It is felt that students of forestry should first know well the commercial species of North America, and then become familiar with the lesser important trees and shrubs of the locality where they may find themselves practicing forestry. The latter must usually be done by the student himself with the aid of a local tree manual. If he has fully appreciated generic characteristics during his training in dendrology, this should not be a difficult procedure. Because this book is not comprhensive for any one portion of the country, it seems best to omit detailed keys and to use instead tables covering family and generic characters.^ Our experience shows that basic information is more readily assimilated in this form. The does not mean that keys are not of primary importance, and considerable time should be spent with them in identifying local material. The authors will greatly appreciate having any errors called to their attention and will also welcome comments or criticism from those using the book in teaching or otherwise. Most of the photographs were taken with one of the modern miniature cameras whose remarkable depth of focus has made possible many otherwise unattainable pictures. William M. Harlow, Ellwood S. Harrar--Syracuse, N.Y., Durham, N.C., August, 1937.