of many of them appear elsewhere. To many others in the Government 

 Printing Office, the Department of Agriculture, and the Congress, grate- 

 ful acknowledgment is made. 



For help and loyalty beyond the terms of their job descriptions, thanks 

 are due to Margaret V. Loyd, the editor's assistant, and Catherine F. 

 George, of the Yearbook staff. 



The drawings and charts were made by Rudolph A. Wendelin, Miss 

 Leta Hughey, Linn A. Forrest, and Harry Rossoll, of the Forest Service; 

 Sidney H. Horn, of Ames, Iowa ; and Joseph H. Stevenson, of the Office of 

 Information. Mr. Wendelin also made the end-paper maps, and Mr. Horn 

 drew many of the illustrations at the heads of the chapters. 



Leland J. Prater, of the Forest Service, supervised the taking of many 

 of the photographs. Working with him were the following members of 

 the Forest Service: Ross Angle, Herbert Armstrong, F. S. Baker, Paul S. 

 Bieler, F. M. Cossitt, Duncan Dunning, Frank Flack, George Griffiths, 

 P. Freeman Heim, Antonio A. Hernandez, Jay Higgins, Ashbel F. Hough, 

 Roger Huff, C. R. Hursh, Wallace I. Hutchinson, Bluford W. Muir, 

 Frederick Simmons, Harry Sperling, C. W. Straus, and Paul J. Zehngraff. 

 Others whose photographs appear are Wilfred J. Mead, of the Bureau of 

 Plant Industry, Soils, and Agricultural Engineering; Bob Branstead, B. C. 

 McLean, and Hermann Postlethwaite, of the Soil Conservation Service ; 

 H. Miller Cowling, Russell B. Clapper, H. J. MacAloney, John M. 

 Miller, and J. E. Patterson, of the Bureau of Entomology and Plant Quar- 

 antine; Ralph E. Lawrence, of Washington, and Dr. Curtis May and 

 Edwin S. Menninger, who took the unusual pictures of tree flowers. 



A word about the organization of the material in the Yearbook. We 

 consider first the tree as a unit, a living thing ; next, the tree as a member 

 of a small group in cities and around homes; finally, trees growing to- 

 gether in wood lots, groves, and forests, large and small. The main section 

 of the book ends with chapters on specific problems and values insects, 

 fire, recreation, wildlife, forestry, and economic importance. 



The last part is intended to furnish additional help lists, charts, tables, 

 a glossary of unusual terms, and references for reading for those who 

 wish to pursue the subject further. For many persons the fourth section 

 will be the most useful of all. 



ALFRED STEFFERUD. 



VIII 



