LUTHER BURBANK 



ing a very striking modification. The ultimate 

 limits of its variation can be determined only by 

 further series of experiments. 



STIMULATING VARIATION 



The modification of the balloon-flower has 

 somewhat exceptional interest, because there is 

 only a single species of the genus Platycodon, to 

 which it belongs, anywhere in the world. 



In other words, this genus is what is called a 

 monotype, and it is a well-recognized fact that 

 flowers belonging to a genus having only a single 

 species, and even to genera having half a dozen 

 species, are relatively little subject to variation. 

 Rightly considered, this is almost axiomatic; be- 

 cause the very fact that there are many species in 

 a genus proves that the representatives of that 

 genus have been variable; else they would not 

 have developed so many different forms, since all 

 members of a genus have sprung from the same 

 ancestry within comparatively recent times. 



The balloon-flower has seemingly been isolated 

 under climatic conditions that have not greatly 

 changed for a long period and hence it has main- 

 tained its specific identity, and the type has become 

 thoroughly fixed. And this fact, as I said, gives 

 added interest to such an experiment as that just 

 outlined, which shows how marked may be the 

 developments that can be produced by selective 



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