260 BREEDING CROP PLANTS 



recommended for self-fertilized crops or more specifically 

 for crops which yield ample seed on selfing. When such a plan 

 is adopted for naturally cross-fertilized crops it becomes necessary 

 to insure selfing by artificial means. By reducing ordinary varieties 

 to pure lines, a much more exhaustive study of the material at hand 

 may be made, and on the basis of this study desirable combina- 

 tions affected by hybridization or pure lines of commerical value 

 may be isolated. The method which is adopted after the isola- 

 tion of homozygous lines through self-fertilization will depend 

 on the degree in which vigor is lost as a result of selfing. That 

 homozygous lines may be isolated in squashes is a demonstrated 

 fact, the result of three years' study as carried on by John Bushnell, 

 of the Minnesota Station. Some lines which are comparatively 

 uniform appear vigorous while others are less vigorous. Types 

 for markedly different characters which are relatively uniform 

 have been isolated. 



