148 THE PRINCIPLES OF AGRICULTURE 



prepared, the roots must search wide and deep 

 for food. 



248. Most of the smaller plants require but 

 about six months in which to grow and to fruit. 

 If, in order to secure nourishment and moisture, 

 the roots are obliged to descend into the cold, 

 hard subsoil, where the plant-food is likely to be 

 least available, neither growth nor fruitage can 

 be satisfactory. Those plants which do not ma- 

 ture until they are five to twenty years of age, as 

 fruit trees, can secure much nourishment from 

 the subsoil, although they secure little in any 

 one growing season. Then, too, trees must se- 

 cure a firm hold on the land, or they will be 

 prostrated by winds. By being obliged to send 

 many of their roots into the cold, firm subsoil 

 through many generations, trees have probably 

 acquired the power of securing more of the tough 

 or unavailable food of the subsoil than plants 

 which live but one season. 



249. Different plants require not only to be 

 planted at different seasons of the year, but at 

 different depths. They demand different meth- 

 ods of preparation of the surface soil. Some 

 do best when placed in loose, warm soil, as, 

 for instance, maize and sweet potatoes ; while 

 others do best when grown on fairly cold and 

 somewhat compacted surface soil, as winter 

 wheat. 



