32 PRINCIPLES OF PLANT BREEDING 



length of stem and wrinkled or smooth seed. In nearly all cases 

 where large numbers of individuals are used in the experiments 

 results similar to those experienced in the formulas are obtained. 



In such experiments it is necessary to consider unit characters 

 only in contrast with each other. When two characters are con- 

 trasted one may prevail over the other and is then said to be a 

 dominant character, and the other over which it prevails is a 

 recessive character. White color in any blossom or plant, as in 

 white corn, is recessive in contrast with any other color. A light 

 color is recessive in contrast with a dark color. Mendel found that 

 in peas round seed was a dominant character and wrinkled seed a 

 recessive character. In wheat the beardless character is dominant 

 over bearded heads. In cotton the long staple is dominant over 

 short staple. 



If D represents the dominant character and R the recessive, 

 the result in the first generations after the cross would be expressed 

 thus: JD+%DR-rV|R. The breaking up of the hybrids in 

 succeeding generations would follow the formulas given in the table. 



Pedigrees are records of lineage or ancestry. It has been very 

 common to keep such record for pure-bred animals. As scientific 

 breeding of plants becomes more common it becomes necessary 

 to keep their records in pedigree form. ' 'Pedigree corn" or ' 'pedi- 

 gree wheat" are strains having a recorded history or ancestry. 

 The terms are sometimes used for farm seeds when the record is 

 very incomplete so far as individuals in the lineage are concerned. 



It must be remembered that a pedigree is no guarantee of 

 quality; but that will depend upon the value of the individuals 

 in the lineage. Stock breeders' associations are formed for each 

 breed of animals for the purpose of keeping such records. They 

 establish and maintain certain rules governing the records. 



Animals' pedigrees are much more exact than those of plants. 

 This is because the breeder learns to know the individuals better, 

 the numbers are fewer, and the cost for the raising of each indi- 

 vidual to maturity is greater. The action of wind and insects in 

 the pollination of plants is difficult to control. Whenever a good 

 strain of plants is established it can be named and this name may 

 be the only record necessary. Such is the case with plants that are 

 readily propagated by grafts, buds, cuttings or other asexual 

 means. The type once fixed may never have the danger of being 

 mixed with other strains, as might be the case if seeds were used. 

 The Grimes Golden apple, for example, was established by chance. 



