THE LAW OF DOMINANCE 339 



characters, to the total, or almost total, exclusion of the other. 

 No intermediate forms appeared. 



Mendel called the character that prevailed dominant, and 

 the character that was suppressed, or apparently suppressed, 

 recessive. And the first big result was that crosses between a 

 plant with the dominant character and a plant with the recessive 

 character yielded offspring all resembling the dominant parent 

 as regards the character in question. Let us for shortness 

 call the parents D and R, and the first result may be expressed 

 in a simple scheme : 



Dc? X R? D? X R<? 



D D 



Thus, when tall varieties and dwarf varieties were crossed the 

 offspring were tall. "Tallness" is the dominant character (D), 

 "dwarfness" the recessive character (R). 



The Law of Splitting or Segregation. — In the next generation 

 the cross-bred plants (products of D and R, or R and D, but 

 all apparently like D) were allowed to fertilise themselves, with 

 the result that their offspring exhibited the two original forms, 

 on the average three dominants to one recessive. Out of 

 1,064 plants, 787 were tall, 277 were dwarfs. 



When these recessive dwarfs were allowed to fertilise them- 

 selves they gave rise to recessives only, for any number of genera- 

 tions. The recessive character bred true. 



When the dominants, on the other hand, were allowed to 

 fertilise themselves, they produced one-third of "pure" domi- 

 nants, which in subsequent generations gave rise to dominants 

 only; and two-thirds of cross-bred dominants, which on self- 

 fertilisation again gave rise to a mixture of dominants and 

 recessives in the proportion of 3 : i. 



