22 



CROSSBREEDING CORN. 



productiveness of this cross seems sufficient to warrant the crossing 

 of these two strains in producing seed for general use in Maryland 

 and Virginia, where conditions similar to those of the tests exist. 



As 1909 seed of the male parent occupied every third or fourth 

 row in all four of the tests, a check or standard is afforded for com- 

 paring the productiveness of all the varieties and crosses. In Table 

 V the varieties and first-generation crosses are classified and arranged 

 in separate columns in the order of their productiveness, the most 

 productive being mentioned first and ranked as 1. In computing 

 the comparative productiveness of the varieties and crosses for this 

 table the yield of a variety is decreased or increased proportionately 



Fig. 1.— Diagram showing the relative production of parent varieties of com and their first-generation 

 crosses in Maryland, 1910: A, Male parent, variation of 1909 seed; B, male parent, mean of 1909 seed; 

 C, mean of crosses; D, variation of crosses; E, male parent, variation of 1908 seed; F, male parent, 

 mean of 1908 seed; G, variation of female parents; H, mean of female parents. 



as the average yield of the two nearest rows of Selection 119 exceeds 

 or falls short of the general average of Selection 119 for all rows in 

 all the tests. 



From the seven best female parents the crosses of six are found 

 among the seven best crosses, Selection 77 being the only high- 

 producing variety whose cross is a poor producer. ^Uong with this 

 indication that the productiveness of the parents influences the 

 productiveness of the cross there are sufficient exceptions to indi- 

 cate that the productiveness of a first-generation cross is sometimes 

 determined to a great degree by other factors. 



218 



