12 
Nebraska Agricultural Exp. Station, Research Bui. 20 
Comparing the low leaf area and high leaf area groups (1) 
before inbreeding, (2) as inbred strains, and (3) as F 1 hybrids 
between these strains, the respective relative values for the fol- 
lowing characters were: (1) Ivatio of leaf area to dry matter, 
82:100, 84:100, and 82:100; (2) actual leaf area per plant, 
77:100, 76:100, and 82:100; (3) total dry matter, 95:100, 94:100, 
and 99:100; (4) ear weight per plant, 99:100, 125:100. and 
107:100. 
These data indicate that the outcome of inbreeding and 
hybridizing experiments may be quite extensively directed thru 
previous selection. 
18. In a two-year test in which seven first and second gen- 
eration hybrids were compared with the original corn, the re- 
spective relative yields were 125, 67, and 100. If the segrega- 
tion of factors pertaining to grain yield should occur in the 
simple Mendelian ratio, the yield of the F 2 hybrids might be ex- 
pected to center between the average of the pure line parents 
and their F t hybrids. During 1916 and 1917 the pure line par- 
ents approximated 24 per cent of the F 1 yield. A theoretical 
F 2 yield intermediate between these pure line and F 1 hybrid 
yields would have been 62 per cent of the hybrid yield, whereas 
the F 2 actually yielded 53 per cent as much. 
These data show very definitely the inadvisability of select- 
ing seed corn from an F 1 hybrid between such pure lines, no 
matter how productive the F, generation may be. 
19. Very different results were obtained from hybrids be- 
tween ordinary commercial varieties. In a four-year test, the 
yield of thirteen variety hybrids averaged 4 per cent less than 
the average of both parents, and 9 per cent less than the best par- 
ent. No hybrid equaled the best variety parent in grain yield. 
This failure of the F, hybrid to be more productive than the aver- 
age of the two parents may be accounted for by the fact that the 
varieties are already fully heterozygous. For the same reason 
the F 2 generation of the variety hybrids yielded fully up to the 
F, generation. All plants of the second generation were as 
heterozygous as were plants of the F, generation. 
In these experiments, seed for the F., generations for both 
pure line and variety hybrids was produced by crossing F, 
plants, and not by self-fertilization. The latter procedure would 
doubtless have reduced the F., variety yield approximately the 
same as the F 2 pure line yield was reduced. The method em- 
ployed in these experiments corresponds to a farmer's procedure 
in selecting seed ears from an F t hybrid field. 
