580 PLANT BREEDING 



features of the two plants used in the cross. Since Mendel's 

 discoveries have furnished principles that make it possible to 

 interpret the behavior of hybrids, one can proceed with consid- 

 erable certainty. As to just how the factors introduced by the 

 sperm and egg will manifest themselves in the offspring resulting 

 from a cross is not known until the offspring appear. The char- 

 acters, whether they blend or behave as dominants and recessives, 

 are identified only by observations of the hybrid generations. The 

 hybrid may be like one parent in some features and like the other 

 parent in other features, or in size and some other characters it 

 may be intermediate between the two parents. According to 

 Mendel's law, we can expect three kinds of individuals in the 

 F2 generation when one pair of contrasting characters is con- 

 sidered, and that the pure dominants and pure recessives will 

 breed true whether one or many pairs of characters are taken 

 into account. The pure dominants and pure recessives can be 

 identified by further breeding, and if they prove to be more 

 desirable than the varieties used in the cross, then by propa- 

 gating them a more desirable race or variety is established. 

 In case one wishes to bring together in one individual a number 

 of desirable characters, some of which are present in one variety 

 and some in another, the breeding process to obtain the indi- 

 viduals pure for these characters is complex, as was shown in 

 the discussion of Mendelism, and the more factors involved, the 

 more complex is the process. But Mendel's law points the 

 way of procedure, and it is possible for the patient plant breeder 

 to so manipulate the breeding through a number of generations 

 as to finally obtain a combination of the desirable characters in 

 an individual that will breed true. The desired individual hav- 

 ing been secured, the new race or variety is practically estab- 

 lished. Much has been accomplished in improving plants 

 through hybridization. For example, in this way a much more 

 desirable race of Wheat has been obtained in England. One 

 variety of English Wheat, yielding well but producing a poor 

 grade of flour, was crossed with a variety of Canadian Wheat, 

 which produces a good grade of flour but does not yield so well 

 in the English climate as the EngUsh variety. The plant breeder 

 finally succeeded in getting a race having the desirable features 

 of producing good flour and yielding well in the English climate. 

 By crossing Wheat, having some desirable qualities but sus- 



