A COMPARISON OF MAIZE-BREEDING METHODS 2s ie 
between selfed lines representing the first, second, and fourth gen- 
erations and the original variety. The highest yield was from the 
first-generation cross of selfed lines. The superiorty of the first- 
generation cross over that of the fourth and the original variety was 
undoubtedly significant and amounted to 40 to 50 per cent. The 
difference between the first-generation seed as compared with that 
of both the second-generation and the crossbred seed probably was 
significant also. The yields of the second-generation and the cross- 
bred seed were practically identical, and both were undoubtedly su- 
perior to either the fourth-generation or the crib-selected seed. From 
indirect comparison it would appear that the crib-selected seed was 
significantly superior to the fourth-generation cross. 
A calculation of the coefficients of inbreeding showed that a nar- 
row inbreeding was not incompatible with high yields. The I; crosses 
from which the highest yields were obtained had an average coeffi- 
cient of inbreeding of 78 per cent relative to the foundation stock. 
The seed stocks resulting from both breeding methods were 
decidedly superior to the original variety. 
Although the highest yields were obtained from the selfed experi- 
ment, a single high-performing selfed line played soimportant a part 
in the final yields that it seems unsafe to consider the results as 
sufficiently typical of the method to warrant recommendations. 
Three types of deleterious variations in maize are recognized, and 
the breeding methods best calculated to eliminate them are discussed. 
LITERATURE CITED 
(1) Bruce, A. B. 
1910. The Mendelian theory of heredity and the augmentation of vigor. 
In Science, vol. 32, pp. 627-628. 
(2) Emerson, R. A. 
1922. The nature of bud variations as indicated by their mode of inheri- 
tance. Jn Amer. Nat., vol. 56, pp. 64-79. 
(3) Jonss, D. F. 
1917. Dominance of linked factors as a means of accounting for heterosis. 
In Genetics, vol. 2, pp. 466-479. 
(4) Kensie, F., and C. Petiew. 
1910. The mode of inheritance of stature and of time of flowering in peas. 
In Jour. Genetics, vol. 1, pp. 47-56. 
(5) Ricusy, F. D. 
1924. Effects of selection on the yield of a cross between varieties of corn. 
U.S. Dept. Agr. Bul. 1209, 20 p., illus. 
WRIGHT, S. 
(6) 1921. Systems of mating. Jn Genetics, vol. 6, pp. 111-178, illus. 
(7) 1922. Coefficients of inbreeding and relationship. Jn Amer. Nat., vol. 56, 
pp. 330-338. 
(8) 1923. Mendelian analysis of the pure breeds of livestock. Jn Jour. Hered- 
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