120 Plant-Breeding 



tions different from nature, or desires a different set of 

 characters. We have seen that nature's chief barriers to 

 hybridization are total refusal of many species to unite, 

 and entire or comparative seedlessness of offspring. 



The notion is somewhat firmly rooted in the popular 

 mind that new varieties can be produced with the greatest 

 ease by crossing parents of given attributes. There is 

 something captivating about the notion. It smacks of a 

 somewhat magic power that man evokes as he passes his 

 wand over the untamed forces of nature. But the wand 

 is often a gilded stick, and is likely to serve no better 

 purpose than the drum major's pretentious baton ! 



Let it be said further that crossing alone can accomplish 

 comparatively little. The chief power in the evolution or 

 progression of plants appears to be selection, or, as Darwin 

 puts it, the law of " preservation of favorable individual 

 differences and variations, and the destruction of those 

 which are injurious." Selection is the force which aug- 

 ments, develops, and fixes types. Man must not only 

 practice a judicious selection of parents from which the 

 cross is to come, which is in reality but the exercise of a 

 choice, but he must constantly select the best from among 

 the crosses, in order to maintain a high degree of usefulness 

 and to make any advancement ; and it sometimes happens 

 that the selection is much more important to the cultivator 

 than the crossing. 



Further discussion of this subject naturally falls under 

 two heads : the improvement of existing types or varieties 

 by means of crossing, and the summary production of new 

 varieties. As already stated, the former office is the more 

 important, and the proposition is easy of proof. It is 



