8o Plant Genetics 



The question arises whether there is any way of 

 avoiding this impossible situation. The escape is sug- 

 gested by the fact that time can take the place of 

 numbers. EAST (2) has shown that by growing 1000 

 individuals in the F 2 generation, 100 in the F 3 , and 

 50 in the F 4 , one stands as much chance of getting the 

 desired combination as by growing 250,000 in the F 2 , 

 provided an intelligent selection is made in each genera- 

 tion. In other words, one who understands the mecha- 

 nism of the inheritance of quantitative characters will 

 grow only 1000 individuals in his F 2 generation and will 

 select for seed only those individuals with the right 

 number of factors. In this way, by intelligent selection, 

 factors are piled up in the right direction from year to 

 year. In a few years the desired result will be reached 

 without the necessity of growing a very large number 

 of individuals. Such work is practicable at experiment 

 stations, and it is the kind of work that a number of them 

 have been doing recently. Even the ordinary farmer 

 should be able to do such work. Although his selection 

 of individuals should not be quite as intelligent as that 

 of a scientific breeder, he would probably be selecting in 

 the right direction and making some advance. A little 

 more time and a little more acreage would bring him 

 to the desired result. 



A further application of the factor hypothesis may be 

 considered. The practice we have been discussing under 

 the name of the inheritance of quantitative characters seems 

 to be little more than what has already been called 

 artificial selection, which is the oldest of all methods of 

 plant breeding. It is a method that was thought to 

 be discredited entirely by the work of DE VRIES (i), 



