- A. J. Pieters, Archibald Dixon Shamel, Benjamin Ralph Stauber, Chalmers Jackson King, Charles Sidney Leete, Charles Walter Collins, F. M. Grant, Fred Earl Keating, Frederick John Pritchard, Frederick Wulling Herbert, George McMillan Darrow, George Wright Hoffman, Harry Eugene Burke, Harvey John MacAloney, Hazel Katherine Stiebeling, Herman Meserve Johnson, Mary E. Sweeny, Neil E. Stevens, Orville Edward May, Oscar Roland Mathews, Perley Spaulding, Robert Claude Wright, Thomas Moore Whiteman, United States. Department of Agriculture, Walter Cochran Davis, Carl Stone Pomeroy, Charlotte Chatfield, Clarence Elbert Clement, George Fordyce Waldo, Harold Frederick Loomis, Horace Terhune Herrick, James Warren Hubbard, John Raymond Hansbrough, John Valentine Schaffner, Louis Henry Burgwald, Ruth Leah Morgan, Verner Ivan Clark, William Solomon Porte, Frank Nelson Harmon
· 1931
- Arthur Henry Senner, Auton William Skuderna, Benjamin Ralph Stauber, Charles Brooks, Clarence Elbert Clement, Curtis Paul Clausen, Edmund Lambert, Edward E. Clayton, Erval Jackson Newcomer, George McMillan Darrow, Glenn Arthur Cumings, Glenn Marsh Smith, James Herbert Beattie, James Robert Dawson, James Warren Hubbard, L. H. Patch, M. McPhail, Marion Bertice McKay, Ralph Edwin Beckett, Rosemary Laughlin Marsh, Rosemary Loughlin, Theodore Bergen Manny, Victor Rickman Boswell, William Doyle Reed, United States. Department of Agriculture, Archie Glenn Van Horn, Charles Evans Cormany, Chester Ihner Bliss, Erskine McFarlane Livingstone, Eugene Taylor Batten, Frederick Wulling Herbert, George Fordyce Waldo, John Gordon Gaines, Austin W. Morrill (Jr.), Lewis Alexander Hurst
· 1932