52 THE METHOD OF DARWIN. 



full of significance. For him it was a histor- 

 ical record, the revelation of a cause, the lurk- 

 ing place of a principle. 



A typical example of his treatment of little 

 exceptional facts is that of "Hero, "the un- 

 usual plant in one of the later generations of 

 self -fertilized plants of Ipomoea purpurea.^ It 

 was a little -larger than the crossed seedlings 

 of the same generation, and the first exception 

 that had arisen, in his many experiments, to 

 the rule that the crossed are superior to the 

 self-fertilized seedlings in size and vigor. It 

 was a little thing, even for an exception, and 

 had occurred only after a very long series had 

 established the rule. It was very fit to suffer 

 the common fate of exceptions, and to be 

 deliberately choked for the benefit of the rule 

 to which it was so inconveniently related. By 

 other hands it would probably have been re- 

 corded and then ignored. Darwin made it the 

 parent of a whole race of exceptions. He 

 found "Hero" to be exceptional, not only in 

 being unusually tall, but in its being highly 

 self -fertile, in its great powers of growth, and in 

 its descendants which were crossed having no 

 advantage over its self-fertilized descendants. 



His aim, as soon as he hit upon a line of 

 1 Effects of Cross- and Self-Fertilization, p. 60. 



