THE CACTUS 107 



of that strange influence which we do not 

 well understand but which we see constantly 

 illustrated, it takes on a new vigor of 

 growth. 



It surpasses the flowers of either one of its 

 immediate ancestors somewhat as the hybrid 

 Royal Walnut tree surpasses its parents in 

 growth. 



This phenomenon of great vigor or tendency 

 to excessive growth developed through hybrid- 

 ization, is, as we have seen, a very common one; 

 its peculiarity in the present instance is merely 

 that here it applies to the flower of the plant 

 alone, whereas elsewhere we have usually seen it 

 apply to the entire structure of the plant, includ- 

 ing at least in some cases (for example the 

 Primus Berry, the Phenomenal Berry, and the 

 Royal Walnut) the fruit as well. 



Let me add that when the Opuntias not quite 

 so diverse in form as the giants and dwarfs were 

 hybridized, the progeny showed the tendency to 

 increased vigor of general growth, not merely to 

 increase of the flower, although productivity was 

 also emphasized. 



Indeed, it is to the fact of such stimulus of 

 growth by hybridization that my success in 

 developing the gigantic races of spineless cactus 

 is due. 



