- Albert Rudolf Leding, Alexander Campbell Martin, Arnon Lewis Mehring, Arthur Henry Senner, Arthur T. Sweet, Auton William Skuderna, Benjamin Ralph Stauber, C. C. Plummer, C. H. Hadley, Chalmers Jackson King, Curtis May, Curtis Paul Clausen, David A. Savage, David Griffiths, Ernest Victor Abbott, Floyd Franklin Smith, Frederick Charles Lincoln, George Arceneaux, Glenn Gardner Hahn, Harold F. Scholz, Harold Glenn Meginnis, Harold Hall McKinney, Harry Baker Humphrey, J. Clark Salyer, James Fitton Couch, James Herbert Beattie, Jenkin William Jones, John Morrison Cooper, John Robert Parker, Kurt Walter Franke, Lewis Alexander Hurst, Mayne Reid Coe, Orator Fuller Cook, Paul George Russell, Paul Mehl, Paul William Miller, R. A. Blanchard, R. T. Balch, Ralph P. Hotis, Robert J. Sim, Robert Max Merrill, Theodore Bergen Manny, United States. Division of Silvics, Walter Ernest Fleming, Wilbur Clifford Edmundson, Wilbur Magruder Hurst, Wilfred Wickes Ballard, William Middleton, United States. Department of Agriculture, Asa Young Willis, Avis Jenkin Peterson, Claude Hope, Frederick William Metzger, I. E. Stokes, Ira Myron Hawley, J. I. Lauritzen, James Robert McCalmont, John Adam Stoehr, John Walter Taylor, Ralph Brownson Bisland, Victor Rickman Boswell, Walter Raymond Humphries, Wayne Crocker Nason, William Ernest Stone, Charles Conrad Krumbhaar, E. E. Hall, Max Raymond Osburn, Roland McKee
· 1933
- Adrian John Pieters, Benjamin Ralph Stauber, Chalmers Jackson King, Charles Walter Collins, Fred Earl Keating, George Wright Hoffman, Hazel Katherine Stiebeling, Mary E. Sweeny, Robert Claude Wright, Walter Cochran Davis, Charlotte Chatfield, Harold Frederick Loomis, John Valentine Schaffner, Ruth Leah Morgan, Thomas Moore Whiteman
· 1931
- Alice Linna Allen Bailey Nightingale, Charles Abel Bennett, Charles Brooks, Charles William Mann, Claude Hope, Dean Humboldt Rose, Dow Dewey Porter, Eloise Blaine Cram, Francis Leo Gerdes, Frederick William Metzger, George W. Barber, Harry Nelson Vinall, Henry Miner Eakin, Irvin Cecil Brown, Katherine Melvina Downey, Norman Julian Wall, Paul Lewis Harding, R. W. Leukel, Robert H. Weidman, Stephen Harold Hastings, Thompson Elwyn Woodward, Verne Lester Harper, William Jeter Phillips, Chalmers Jackson King, Charles Lincoln Powell, Cyril Oliver Bratley, E. A. Gorman, Glen Blaine Ramsey, Horace Greeley Byers, J. C. Stephens, Lenthall Wyman, Ralph P. Hotis, Warren W. Maines, William Cecil Cooper, John Holmes Martin, Lacy Porter McColloch, Orlan Parker, R. R. Graves
· 1936
- Alexander Campbell Martin, Arthur Henry Senner, C. C. Plummer, C. H. Hadley, Chalmers Jackson King, Curtis Paul Clausen, David A. Savage, Ernest Victor Abbott, Frederick Charles Lincoln, Glenn Gardner Hahn, Harold Francis Scholz, Harold Glenn Meginnis, J. Clark Salyer, James Herbert Beattie, Jenkin William Jones, Mayne Reid Coe, Paul William Miller, Ralph P. Hotis, Robert J. Sim, United States. Department of Agriculture, Walter Ernest Fleming, Wilbur Clifford Edmundson, Wilbur Magruder Hurst, Claude Hope, Frederick William Metzger, Ira Myron Hawley, James Robert McCalmont, John Walter Taylor, Victor Rickman Boswell, Walter Raymond Humphries, William Ernest Stone, E. E. Hall, Max Raymond Osburn, Roland McKee
· 1934
- Albert Ronald Merz, Auton William Skuderna, B. L. Wade, Bess Viemont Morrison, Chalmers Jackson King, Charles Frederick Clark, Charles W. Culpepper, Clark Frederick Clark, David A. Savage, Elmer Valentine Walter, Ernest Muchmore Mervine, Fred Corry Bishopp, George Washington Craddock, Helen Nebeker Hann, Joseph Stuart Caldwell, Joshua John Skinner, Leo Anthony Isaac, Loyd William Brannon, Oscar Roland Mathews, Paul A. Berry, Rufus King Helphenstine, Samuel Newton Dicken, United States. Department of Agriculture, Victor Rickman Boswell, Wilbur Clifford Edmundson, William Daniel Smith, Hazel Katherine Stiebeling, Arthur Otto Alben, Carroll Newton Smith, Frederick James Stevenson, Hubert Hill Moon, James Herbert Beattie, Lee Seaton, Lindsey Andrew Brown, Margaret Blanche Hays, Ralph Edwin Beckett, Stanley Ward McBirney, Adonis A. Mathewson, Earl Donald Fowler, John McDowell McCown, Orlan Parker
· 1939