Neo-Mendelism 47 



There are two other types of blending inheritance that 

 may be mentioned, the mechanism involved in which will 

 be discussed in another connection. 



After the first announcement by CORRENS of simple 

 blending inheritance further investigation revealed 

 many similar cases; in fact it was soon regarded to be a 

 common phenomenon that the F x should be an inter- 

 mediate. At the same time it was fully expected in such 

 cases that the hybrid would split in the F 2 generation 

 in a 1:2:1 ratio. Practical breeders were advised that 

 Mendel's law was invariable; that a hybrid must split; 

 and therefore that the only way to preserve a valuable 

 hybrid was by vegetative propagation. Many breeders 

 realized the value of this advice, but some reported cer- 

 tain surprising results. They claimed that they had 

 made numerous crosses and that in many cases the 

 intermediate F t individuals continued to breed true to 

 the intermediate hybrid characters, even when propa- 

 gated from seed. Gardeners today continue to tell of 

 certain Begonia hybrids that continue to breed true from 

 seed in intermediate condition. BURBANK (2) claims 

 many such cases, in which hybrid blends breed true to 

 seed, as did their parents. All such claims contradicted 

 the experience of scientific breeders and seem to destroy 

 their theories. Accordingly, the Mendelians sought to 

 explain these claims of pure-breeding hybrids and suc- 

 ceeded in doing so remarkably soon. There has been 

 much discussion of this situation and there is no need to 

 go into the details of it. It will be sufficient to mention 

 briefly the principal methods by which pure-breeding 

 hybrids have been explained as not contradicting 

 Mendel's law. 



