Neo-Mendelism 57 



rather of a plant as a complex physico-chemical labora- 

 tory. No one claims that all chemical reactions are 

 useful; they are simply inevitable; and plant characters 

 are the result of chemical reactions and physical necessi- 

 ties. Even though we assume the simultaneous origin 

 of two complementary factors, they would have to be put 

 on separate chromosomes, for the factors are separately 

 inherited. 



The other alternative is to suppose that these factors 

 originated independently in the history of a plant. In 

 this case, of course, the first one to be produced would 

 remain functionless until finally its complement came 

 into existence. This might be an explanation of what 

 are called latent characters. Also they might have not 

 only originated independently but in different varieties 

 or species. In this case if natural hybridizing should 

 bring them together the result would be the appearance 

 of a new character, and this may have been a very im- 

 portant factor in the origin of species. 



This may serve as an introduction to the factor 

 hypothesis, with complementary factors as an illus- 

 tation, simply because it is the simplest situation. There 

 are many other kinds of factors recognized, but we shall 

 not attempt to Ust all of the proposed types. A simple 

 illustration of the better known types is as follows: 



a) A complementary factor is added to a dissimilar 

 factor to produce a particular character. 



b) An inhibitory factor prevents the action of some 

 other factor. 



c) A supplementary factor is added to a dissimilar 

 factor with the result that the character is modified in 

 some way. 



