150 PLANT-BREEDING 



than average value. The entire breeding plot has been 

 started with the purpose of comparing the hereditary qualities 

 of the mother ears, and in estimating the result one should 

 stick to this principle. Excellent specimens in bad rows 

 may owe their qualities to cross- fertilization of the seed from 

 which they sprang, or to accidentally good environmental 

 conditions during their development, but in both cases they 

 have to be rejected. 



Next comes the question, how many rows should be 

 selected for the continuance of the breeding culture? Of 

 course, only one of them can be the very best, and if it were 

 possible to select this without mistake, there could not be 

 any doubt about the validity of the principle of choosing 

 one single row. But the experience of the Svalof Station 

 shows that even for the ordinary cereals such a definite 

 judgment can but rarely be obtained by one year's trial. 

 In compliance with these considerations, practical corn 

 breeders usually choose ten champion rows and start the 

 breeding plot of the next year with their seed. Records are 

 kept and the origin of the mother ears of each new row can 

 be traced. By this means a comparison of the hereditary 

 qualities of the grandmother ears will be possible, and this 

 will prove to be very helpful in the selection of the second 

 year. A most complete analogy with the Svalof method 

 will thus lead to correspondingly valuable results. 



Concerning continuous or repeated selection, many corn 

 breeders in the United States have the same views as the 

 German breeders of wheat and other cereals. They sur- 

 mise that by careful, continued selection, definite characters 

 can be bred into the strains, according to the wishes and 

 needs of the farmers. This is the theory of slow improve- 

 ment, which has obtained such a large influence since Dar- 

 win built upon it one of the main supports of his doctrine 

 of evolution. In the case of the rye of Schlanstedt, described 



