Inlieritance in the Higher Plants 89 



In general one may say that when two individuals are 

 crossed which differ from each other in paired characters, 

 of which one can usually be interpreted as the absence of 

 the other, these parental characters reappear in the second 

 hybrid generation unchanged in vigor and in potency. 

 The first hybrid generation may be exactly like one parent 

 in any particular character, in which case that character 

 is completely dominant; or, the hybrid may be interme- 

 diate between the two parents in that character, in which 

 case dominance is incomplete or absent. Of these two 

 phenomena the behavior of the second hybrid generation 

 is by far the most important. The parental characters 

 are reproduced in it in constant ratios; and it is believed 

 that this could only come about if the factors that represent 

 these characters in the germ cells of the hybrid occur there 

 unchanged and in equal numbers. Generalize this view- 

 point and we have the belief that organisms behave in 

 heredit)' as if they were mosaics of character units, each 

 unit being represented in the germ cell by one or more 

 factors of unknown nature. These factors are commonly 

 transmitted independently of one another, and upon them 

 depend the characters of the individuals to which they give 

 rise. 



Stated in fewer words, the essential feature of Mende- 

 lianism is the segregation of potential characters in the 

 gamete in a state of apparent purity, and their recombina- 

 tion by the law of chance through random mating. The 

 term " Mendelian notation" was therefore used advisedly. 

 Mendelian notation is a simple interpretation of certain 

 facts of heredity obtained in pedigree cultures. It is a con- 

 venient notation and is used much as the element symbols 

 are used in chemistry. It makes no difference to analytical 



