ACKNOWLEDGMENTS 



The following individuals and institutions have sup- 

 plied illustrations referred to by the figure numbers 

 opposite their names. 



Prof. W. G. Brierley, University of Minnesota at St. Paul 



107, 108, 110, 114, 116, 118 

 California Experiment Station at Berkeley 



257, 258, 265, 282 to 286, 288 to 290 



Colorado Experiment Station at Fort Collins 72, 136a 



Connecticut Experiment Station at Storrs 



25 to 27, 209, 215, 216, 302 

 Cornell Experiment Station at Ithaca, N. Y. 



211 to 213, 183 (redrawn by B. F. Williamson) 

 Prof. A. W. Cowell, Pennsylvania State College at State College, 



Pa. 95, 304, 307, 311, 312 



Credit lost 24 



Farmers' Bulletins of the United States Department of Agri- 

 culture 181, 188, 190, 248, 254 to 256, 259 to 262, 264, 266, 

 274, 276 to 281, 287 



N. R. Graves of Rochester, N. Y. 298 to 300 



Idaho Experiment Station at Moscow 75 to 77, 92, 93 



Indiana Experiment Station at Lafayette 



61, 73, 132 to 134, 178, 179 



Iowa Experiment Station at Ames 70 



E. D. Kains of Wyomissing, Pa. 64, 65, 96, 310 



Kentucky Experiment Station at Lexington 269 to 273 



Maryland Experiment Station at College Park 22, 102 



A. F. Mason of State College, Pa. 2 



Massachusetts Experiment Station at Amherst 313 



Missouri Experiment Station at Columbia 



98, 120, 214, 217 to 225, 294 

 New Jersey Experiment Station at New Brunswick 



121, 122, 125, 128 to 131, 195 to 198, 200 



New York Experiment Station at Geneva 74, 275 



North Carolina Experiment Station at Raleigh 33 



Ohio Experiment Station at Wooster 4, 315 to 324 



xi 



