The ^discoveries of Four Great botanists 



H, and thus fertilizes it. Doubtless he will do the 

 same for the stio:ma of G when it matures. 



Not only did Darwin's theory solve the first mys- 

 tery which Sprengel left unexplained, but it was 

 equally successful in untanglincr the second knot. 



No reason could be given why fertilization by 

 insects, according to the theory of Sprengel, was 



G Fig. 6. H 



preferable to self-fertilization ; but, as Darwin soon 

 proved by actual experiment, cross-fertilization is a 

 distinct advantage to the flower, in the competitive 

 struggle for existence, all cross-fertilized flowers pro- 

 ducino^ healthier seed than self-fertilized ones. Cross- 

 fertilized flowers, therefore, are the final result of 

 natural selection, or the law of the survival of the 

 fittest. 



HOW X AT URAL SELECTIOX PERFECTS THE FLOWERS 



To illustrate how this law has worked in the de- 

 velopment of cross-fertilized flowers, let us suppose, 



13 



