LUTHER BURBANK 



esting aspect of heredity to which we referred at 

 the beginning of this chapter the phase com- 

 monly spoken of as Mendelism. The essential 

 characteristic of this aspect of heredity, as we have 

 pointed out over and over, is that heritable charac- 

 teristics are transmitted in a sense independently 

 one of another, in such a way that they may be 

 segregated and put together again in new com- 

 binations in successive generations. 



The detail within this scheme of transmission, 

 with which Mendel himself was chiefly concerned, 

 and which absorbed the attention of his followers 

 until it was found that there was need of taking a 

 wider view, was involved in the phenomena of 

 dominance and recessiveness. Mendel found, for 

 instance, as we are aware, that when a tall pea 

 vine was crossed with a short one the hybrids of 

 the first generation were all tall, because, as he 

 said, tallness was dominant and shortness reces- 

 sive. And in the second generation one-fourth of 

 the vines were short because the factors for short- 

 ness were segregated, according to the theory oJ 

 chances, and one-fourth of the vines were pur< 

 recessives. 



The fact of such dominance and recessiven< 

 between pairs of heritable characters is too ob- 

 vious to escape attention of any careful practical 

 experimenter, now that attention has been calle, 



[220] 



