102 AMERICAN BREEDERS MAGAZINE. 



sure that the results of such investigations will lead to the adoption 

 of some hybridization method in the breeding of this crop. 



My experiments with corn during the last year have again given 

 the fullest confirmation of my theories regarding the complex hybridity 

 of the plants which compose an ordinary field of corn as grown at 

 the present time; and data have also been secured having a direct 

 bearing upon the applicability and importance of hybridization methods 

 in corn breeding. Last year I presented the results of a single pair 

 of reciprocal crosses between two self-fertilized strains which I called 

 strain A and strain B. Those strains in hybrid combination produced 

 a yield a little larger than ,the average of those families which had 

 not been self-fertilized, but the difference was very slight. As strains 

 A and B had been essentially unselected, being the first two self- 

 fertilized strains which had become nearly pure-bred, it was antici- 

 pated that a larger number of crosses would discover some strains 

 much superior to A and B as parents of a high-yielding F x hybrid 

 progeny, as well, perhaps, 'as some which are inferior. This belief 

 has been fully supported by the results secured in 1909, for in eight 

 different hybrid combinations which were tested during the past sea- 

 son three have proved better than the combination between strains A 

 and B ; one other combination, also having strain A as one of the pa- 

 rents, gave a result about equal to that of A and B, and three combina- 

 tions produced somewhat less than those of strains A and B. Not all 

 of these hybrid families produced higher yields than the corresponding 

 cultures which had never been self-fertilized, but the three highest 

 yields produced in all my cultures were the result of hybridizing self- 

 fertilized strains which had been, no doubt, reduced nearly to a homozy- 

 gous (pure-bred) state. The average of all the hybrids when compared 

 with the average of all the corresponding cross-bred^ families shows 

 the yield of the former to be only insignificantly lower than that of 

 the latter, these averages being respectively 78.9 bushels per acre from 

 the hybrids/and 79.4 bushels per acre from the cross-breds. This shows 

 how effectively the cumulative "injurious effects" of five years of self- 

 fertilization may disappear in a single year as the result of crossing. 



The large yield of two of my hybrid strains as compared with 

 the product of the best cross-bred families is not a mere chance rela- 

 tion, but is a specific function of the particular hybrid combination 



d I use the term "cross-bred" here to denote those families in which all self- 

 fertilization has been prevented during the five years these investigations have been 

 in progress. 



