UTILIZATION OF HYBRIDS IN PLANT BREEDING 



359 



TABLE LII. YIELDS OF 16 MAIZE CROSSES COMPARED WITH 

 PARENTAL YIELDS. (After Collins.) 



(a) Where the yield of either parent fell as low as 0.10 pound per plant the percent- 

 age of increase of the hybrid is omitted. In dealing with these small quantities it is 

 believed that percentages would be misleading. 



The superior qualities of first-generation hybrids in maize as set 

 forth by Collins may be summarized as follows: (1) Increased yield. (2) 

 Uniformity equal to that of the parents. (3) Quality intermediate 

 between parents (but Hayes' data indicate complete dominance of low 

 protein over high protein). (4) Increased immunity from disease. 

 (5) Extension of the industry into new territory. Especially strong 

 evidence for this is found in several of the crosses between diverse types. 

 " Almost without regard to the nature of the parents the hybrids remained 

 dark green and vigorous when nearly all the pure strains were giving 

 evidence of the lack of moisture by their curved leaves and yellow 

 color." (6) Less localization of highly bred strains. The importance 

 of local adjustment in highly bred strains is the chief reason for the 

 disappointment which sweet corn growers experience when they purchase 

 carefully selected strains from other localities. "First-generation 

 hybrids are to a great extent independent of this delicate adjustment to 

 local conditions." (7) Increased utilization of the work of experienced 



