Multiplication of Extremes 759 



ordinarily difficult, if not impossible, to discern 

 the part which each of the three great branches 

 of variability has taken in the origination of the 

 product. A full analysis is rarely possible, and 

 the treatment of one of the three factors must 

 necessarily remain incomplete. 



Notwithstanding these considerations, I will 

 now give some examples in order to show that 

 fluctuating variability plays a prominent part in 

 these improvements. Of course it is the third 

 in importance in the series. First comes the 

 choice of the material from the assemblage of 

 species, elementary species and varieties. 

 Hybridization comes next in importance. But 

 even the hybrids of the best parents may be im- 

 proved, because they are no less subject to 

 Quetelet's law than any other strain. Any 

 large number of hybrids of the same ancestry 

 will prove this, and often the excellency of a 

 hybrid variety depends chiefly, or at least defi- 

 nitely, on the selection of the best individuals. 

 Being propagated only in a vegetative way, they 

 retain their original good qualities through all 

 further culture and multiplication. 



As an illustrative example I will take the 

 genus Canna. Originally cultivated for its 

 large and bright foliage only, it has since be- 

 come a flowering plant of value. Our garden 

 strains have originated by the crossing of 



