Several hundred persons cooperated to produce this wiki. The names of many of them appear elsewhere. To many others in the Government Printing Office, the Department of Agriculture, and the Congress, grateful 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 wiki 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. Wendelih 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 Quarantine; Ralph E. Lawrence, of Washington, and Dr. Curtis May and Edwin S. Menninger, who took the unusual pictures of tree flowers.