30 VALUE or FIBST-GE^'EKATIO^' HYBEIDS IN CORN. 



Experiments by the writer with primitive tj-pes crossed with one another and with 

 United States varieties, first reported in the present paper, gave increased yields in 1-4 

 out of 16 cases, the average increase being 53 per cent. 



Though the average of the yields of the parent varieties may be 

 considered as a fair standard for judging the increased yields of the 

 hybrids from the standpoint of heredity, the practical value of 

 hybrids must be determined by comparing their yields with those of 

 the more productive parents. To secure evidence on this point it \s-ill 

 be necessary to consider the crosses wliich have been made between 

 good-yielding varieties gro^vn under favorable conditions, excluding 

 those in which there is great disparity in the yields of the parents. 



The following table includes all the crosses here reported in which 

 the parents appear to have been fair-yielding standard varieties 

 giving approximately the same yields. 



Table V. — Increased yield of hybrid corn over the more productive parent. 



Percentage 



of increase 



of hybrid 



over better 



parent. 



Beal (p. 11). ''Varieties essentially alite" 



Beal (p. 11). "Varieties essentially alike" 



Beal (p. 12). Hybrid compared only with, better parent 



IngersoU (p. 12). Strains of the same variety 



Morrow and Gardner (p. 15). Parents differed by 2.6 bushels per acre. . 

 Morrow and Gardner (p. 15). Parents differed by 15.0 bushels per acre. 

 Morrow and Gardner (p. 15). Parents differed by 8.5 bushels per acre. . 

 Morrow and Gardner (p. 15). Parents differed by 13.0 bushels per acre. 

 Morrow and Gardner (p. 15). Parents differed by 5.8 bushels per acre.. 



51 



10 

 21 

 95 







—8 



17 



4 

 18 



It will be seen fi-om Table V that in six of the nine crosses signifi- 

 cant increases were obtained over the yield of either parent, and two of 

 the tlu'ee exceptions should, perhaps, have been excluded, since the 

 differences between the }4elds of the parents were 15 and 13 bushels, 

 respectively. 



The experiments thus far reported are too few to warrant any 

 conclusions regardins: the nature of the crosses wliich mav be rehed 

 upon to yield the greatest increase. It is naturally to be expected 

 that the percentage of increase will be greatest between low-yieldmg 

 strains, but the greatest increase in bushels per acre may follow the 

 crossing of the more highly developed strains. 



Probably none of the crosses here considered were between care- 

 fully bred and locally adjusted strains, ^liat the results of such 

 crosses will be is yet to be determined.. Since the most carefuUy 

 selected strains are more or less inbred, a substantial increase would 

 be expected from crossing two such unrelated inbred strains unless 

 they have already approached the limit of production of the com 

 plant. 



191 



