SOME PRINCIPLES OF PLANT BREEDING 505 



come from widely different localities. For example, seed of 

 a given variety obtained from a distant locality is planted 

 in a given locality where the same variety is stable. The 

 breeder cross-pollinates these with the individuals of the same 

 variety in his own locality, which is apt to induce still greater 

 variation. 



676. A definite purpose in crossing. The plant breeder 

 usually works for a definite purpose in view. Sometimes it is 

 possible to predict results, i.e., to form an idea, or a picture, several 

 years in advance, of the shape and quality of the plant product 

 desired. For example, seedsmen have on several occasions 

 described to plant breeders the character and quality of a wholly 

 new variety of beans which they believed would possess especial 

 commercial merit. The plant breeder was asked how long it 

 would take to breed this variety, and being told that it could be 

 produced in about three years, the seedsman advertised the seed 

 in advance of the existence of the variety. It is rare, however, 

 that the breeder can work with such precision as to determine 

 the time at which the desired result can be obtained except in 

 dealing with varieties whose variations in different directions are 

 already known to him, and by knowing the variations and plas- 

 ticity of his material he can select during several years for this 

 one result. 



677. Work for one thing at a time. The experience of most 

 breeders leads them to work for one thing at a time, since if the 

 breeder selects his plants for several qualities, progress towards 

 excellence in one direction is impeded and often defeated because 

 of some antagonism in the strain he is working on between some 

 of the qualities he is striving to develop. When the desired 

 excellence is reached in regard to one quality, plants possessing 

 this quality are then bred for another quality. If certain of the 

 desired qualities cannot be obtained from this variety by selec- 

 tion, it is then crossed with some closely related variety possessing 

 this character and selection is again resorted to until the plant 

 and productivity as a whole has been brought to the highest state 

 of excellence, or the state of excellence desired. Selection may be 



