HYBRIDS AND CENTRALIZED SEED PRODUCTION. 33 



depend upon the vigor of the phmts; Nothing approaching immunity 

 to this disease lias been observed in any of the varieties or the hybrids.'^ 



FIRST-GENERATION HYBRIDS AND CENTRALIZED SEED 



PRODUCTION. 



It is coming to be generally recognized that in corn culture the use 

 of seed not produced locally is a bad practice, and this is especially 

 true of the most carefully selected varieties. The stimulus to the 

 production of high-grade strains of corn is seriously weakened by the 

 extremely circumscribed area in which such strains can be grown 

 advantageously without further selection. Men of exceptional skill 

 and experience who devote their whole time to the development of 

 improved strains can, without doubt, do more effective work in selec- 

 tion than the farmer who is pressed with other work. But as soon as 

 a carefully selected strain is placed under conditions different from 

 those under which it was developed it behaves in a more or less 

 abnormal manner, and appears at a disadvantage when compared with 

 locally adjusted varieties. This factor of local adjustment is so 

 important that if carefully selected strains are to be directly utilized 

 in commercial production the centralization of seed growing must be 

 discouraged. Farmers must be urged to select their own seed or to 

 secure it from a local breeder. 



That first-generation hybrids are relatively free from the new-place 

 effects that so seriously interfere with the spread of varieties has not 

 been demonstrated in corn, but may confidently be expected from the 

 analogy of first-generation hybrids in other crops.'' This does not 

 mean that a given cross will do equally well in all parts of the country, 

 but that it will make little difference whether the crossing is done in 

 one part of the country or another. When it is once ascertained which 

 combination of varieties is best adapted to a particular locality, pure 

 seed of these varieties may be maintained and the crosses made under 

 the supervision of a trained plant breeder at a central station. 



« It was repeatedly observed that plants affected with smut were darker green and 

 more vigorous than neighboring plants not affected. This difference was noticed 

 especially in a strain that had been reduced in vigor by self-fertilization. In this case 

 but one plant in the row was affected with smut, and the stalk of this plant measured 

 3.82 inches in circumference, while the largest of the healthy plants measured only 

 3.15 inches. The leaves were also broader and dark green, while all the other plants 

 were yellow and spotted. 



Except for the deformed parts where the fungus fruited, the smutted jilant appeared 

 more nearly normal than any of the others. The presence of the fungus seems in some 

 way to restore the vigor lost through self-fertilization. 



b Cook, O. F. Local Adjustment of Cotton Varieties. Bulletin 159, Bureau of Plant 

 Industry, U. S. Dept. of Agriculture, 1909. 

 191 



