62 CROSSBREEDING CORN. 



It will be seen that seven varieties equal or excel Marlboro Pro- 

 lific. Wlien these seven varieties are crossed with Marlboro Prolific 

 as sire six out of the seven first-generation crosses exceed the Marl- 

 boro Prolific in grain production, and five in stover production. 



It will also be seen that two varieties equal or excel Rodgers White 

 Dent. Wlien these two varieties are crossed with Rodgers Wliite 

 Dent as sire both of the first-generation crosses exceed the Rodgers 

 White Dent in grain and stover production. It will thus be seen 

 that out of the 20 crosses made 8 have given grain yields greater 

 than the better parent, and 7 have given stover yields greater than 

 the better parent. 



RELATION OF THE PRODUCTIVITY OF THE CROSSES TO THE PRODUCTIVITY OF THE 



PURE STRAINS. 



It is a striking point in connection with the foregoing table that 

 aU those female varieties giving more productive crosses than either 

 parent are grouped at one end — the upper end — of the ranking list 

 for production and with but one break in the rank. None fall below 

 fourth in production in a total ranking of seven. With one excep- 

 tion the varieties that can not be said to have given advantageous 

 crosses with either sire are grouped at the other or lower end of the 

 ranking list. 



Omitting Marlboro Prolific and Rodgers Wliite Dent, nine other 

 varieties are crossed by each of these sires. In six out of the nine 

 comparisons the crosses with Rodgers Wliite Dent are more productive 

 than those mth Marlboro Prolific. 



In view of these points and the fact that Rodgers Wliite Dent is 

 more productive than Marlboro Prolific it is found that the pro- 

 ductiveness of both parents seems to stand out clearly as a factor 

 in influencmg high yield in first-generation crosses. 



The Tindal variety, however, is a striking exception to this seem- 

 ing tendency. The rank of this variety is third in productiveness, 

 but when crossed by Marlboro Prolific its yield was actually less 

 than its poorest producing parent; and when crossed by Rodgers 

 White Dent the cross was less productive than that sire. 



Because of this exception, this apparent tendency can not be relied 

 upon as a guide in the selection of suitable varieties for practical 

 crossing. 



ADAPTATION AS A FACTOR IN THE PRODUCTION OF HIGHER YIELDS THROUGH 



CROSSING. 



As the difference between the lowest and the highest producers 

 is less than 5 bushels per acre, it would seem that it might be ques- 

 tionable to dicuss this subject with the data at hand. In justice 

 to the subject, however, it should be stated that the appearance of 

 the corn produced indicated more variabihty in adaptation than do 

 the weights. 



218 



