66 CROSSBREEDING CORN. 



cation of what can be accomplished in the field of research and more 

 especially in estabHsliing methods of producing high-j-ielding seed 



corn. 



The influences that show with the greatest uniformity in these 

 tests are those of acchmatization and adaptation. The results 

 given here of these influences will be combined in a future publication 

 with results obtained in other localities showing the effects on maize of 

 acclimatization and adaptation. In studj^ing the effects attributable 

 to crossbreeding it is necessary to recognize the effects due both to 

 acchmatization and to adaptation. The distinction between the 

 effects of acclhnatization and of adaptation is brought out in the 

 tests of identically the same lots of seed in Maryland and in Cali- 

 fornia. In Maryland, because of their acclimatization and adaptation 

 some varieties produced much better than others of the same growing 

 period which were brought from distant States. None of these 

 varieties were acclimated to Cahfornia conditions, though some of 

 the earliest maturing, which were least productive in Maryland, were 

 most productive in California. Their early maturity proved an 

 adaptation which enabled them to escape the later and drier part of 

 the summer. In Texas, varieties that have been subjected for years 

 to practically the same chmatic conditions indicate different degrees 

 of adaptation to clay soils and to sandy soils. 



Tests of this nature thus far reported indicate that first-generation 

 crosses usually produce better than the average of the two parents. It 

 is not certain that this is entirely due to the advantages that these tests 

 have given to the crosses regarding age and vitality of seed, or to the 

 year of adaptation and selection incident to growing the crossbred 

 seed under the same environment in which the test of productiveness 

 was afterwards made, but to which the parent varieties were not 

 adapted. If further tests should show that with all conditions 

 equalized there still exists a tendency for first-generation crosses to 

 produce betfer than the average of the two parents, it might be taken 

 as an indication that the higher yielding parent is usually prepotent. 



A production better than the average of the two parents, unless 

 it be better than the production of either parent, would furnish no 

 practical method of originating strains superior to those already 

 existing, except in cases in which the crossing might originate strains 

 that combine or nick better than previously existing strains. When 

 all influencing factors, such as age and maturity of seed, acchmatiza- 

 tion, and adaptation are equal, and the first-generation cross is more 

 productive than either parent, it is a clear instance in which a prac- 

 tical advantage is derived by crossbreeding. 



Variations found to apply to varieties are also found to apply to 

 different ears within a variety when they are crossbred and tested 

 separately — in other words, some ears arc crossed with another 



218 



