CONTENTS XV 



expression of the law, 219 ; Unit characters, 220 ; Dom- 

 inants and recessives, 221 ; Occurrence of aberrant forms, 

 222 ; Correlation of characters, 223 ; Examples of cor- 

 relation, 224 ; Discrimination in cereal breeding, 225 ; 

 Method of cross-pollination, 226 ; Accompanying details, 

 227 ; Limits of hybridization, 228 ; Composite crossing, 

 229 ; Pringle's hybrids, 230 ; Work of Blount, 231 ; Ful- 

 caster wheat, 232 ; Work of Jones, 233 ; Work in 

 Canada, 234 ; Marquis wheat, 235 ; Work of Rimpau, 

 236 ; Garten's hybrids, 237 ; Examples of the Garton 

 hybrids, 238 ; Work of the United States Department 

 of Agriculture, 239 ; Examples of United States hybrids, 

 240 ; Work of Farrer, 241 ; Farrer's principal hybrids, 

 242 ; Other Australian hybrids, 243. 



PART II. CEREAL ENVIRONMENT 



CHAPTER X 



SOIL RELATIONS 233-253 



Favorable soil environment, 244 ; Prairie soils, 245 ; 

 Mineral bases, phosphates and nitrogen, 246 ; Humus, 

 247 ; Importance of lime, 248 ; The origin of prairies, 

 249 ; The Russian chernozem, 250; Soil divisions of the 

 chernozem, 251 ; The Great Plains of North America, 

 252 ; Depth of soil, 263 ; The Argentine Pampas, 254 ; 

 Prairie and steppe cover, 255 ; Chemical composition of 

 prairie soils, 256 ; Mechanical analysis of prairie soils, 

 257 ; Other large cereal areas, 258 ; The subsoil, 259 ; 

 Soil water, 260 ; Variation in water supply in different 

 soils, 261 ; Sandy versus heavy soils, 262 ; The moisture 

 equivalent of different soils, 263 ; Application of the prin- 

 ciple to different soils, 264 ; The wilting coefficient, 265 ; 

 Alkalinity of the soil, 266 ; Alkali tolerance in cereals, 



267 ; Pot experiments on cereal tolerance of alkalies, 



268 ; The calcium-magnesium ratio, 269 ; Soil tempera- 

 ture, 270. 



