SELECTIONS 329 
The futility of attempting to generalize regarding the effects of selec- 
tions in plants must be obvious from what we now know about the com- 
position of plant populations. With the application of Johannsen’s 
genotype conception in analyzing the composition of a field of maize the 
problem of explaining the réle of selection in the Illinois corn breeding 
experiments was immediately simplified. This was perceived by Shull 
who pointed out that the results of these experiments might be readily 
explained on the ground that some hybrid combinations of genotypes 
have greater capacity for the production of the desired qualities than 
other combinations, and that the selection has gradually brought about 
Fig. 135.—Result of selecting corn for high and low ears during 5 generations. The 
white tape marks the position of the ears on the front row of plants in both plots. 
the segregation of those genotype combinations which had the highest 
capacity for the production of the desired quality. 
Meanwhile Surface had made an illuminating analysis of the data 
from the first 10 years of selection as reported by Smith. This treatment 
is so valuable as to warrant its examination in some detail. At the time 
the selections were made a careful record of the pedigree of each ear was 
kept. These pedigrees are of course for the maternal side only since 
self-pollination was not practised. From these data Surface prepared a 
pedigree chart for each of the four strains. The chart for the high- 
protein strain is reproduced in Tables XLVIII and XLIX. As stated 
above 24 ears containing the highest per cent. of protein were selected for 
the 163 ears analyzed in 1896. These were given registry numbers from 
101 to 124 inclusive as shown in column one of the two tables. For 
convenience we may refer to these ears as the first generation of high- 
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