234 AGRICULTURE 



called variation, which means that although 

 the progeny resemble the parents, the re- 

 semblance is never quite complete. Without 

 variation there can be no improvement. 

 Variation may mean much or little, it may 

 imply some small divergence from the original 

 type, which is so inconspicuous as to be 

 impossible or difficult of detection ; or it 

 may mean a sharp departure from the 

 original type, in which case it may merit 

 the term " mutation " or " sport." Sports 

 may instantly give rise to a new breed, 

 whereas, in the method of improvement by 

 selection throughout a series of generations 

 the breed is secured slowly and with more 

 difficulty. Animals more than plants fre- 

 quently show a tendency to reversion or 

 atavism, which means that the organism is 

 reproducing certain characters possessed by 

 an ancestor, but not by an immediate parent. 

 The ancestor may be no further back than 

 two or three generations, or it may be much 

 more remote. 



In the practice of breeding, no matter 

 which line is adopted, one must see that the 

 individual plants one propagates from year 

 to year are given precisely similar conditions 

 of growth, because it is only by attending 

 to this matter that one can be sure that 



