LECTURE XVII 



THE PRODUCTION OF DOUBLE FLOWERS 



Mutations occur as often among cultivated 

 plants as among those in the wild state. Gar- 

 den flowers are known to vary markedly. 

 Much of their variability, however, is due to 

 hybridism, and the combination of characters 

 previously separate has a value for the breeder 

 nearly equal the production of really new qual- 

 ities. Nevertheless there is no doubt that some 

 new characters appear from time to time. 



In a previous lecture we have seen that 

 varietal characters have many features in com- 

 mon. One of them is their frequent recur- 

 rence both in the same and in other, often very 

 distantly related, species. This recurrence is an 

 important factor in the choice of the material 

 for an experimental investigation of the nature 

 of mutations. 



Some varieties are reputed to occur more 

 often and more readily than others. White-col- 

 ored varieties, though so very common, seem to 

 be of ancient date, as a rule, but only few have 



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