SELECTION 335 
quite so striking. In the low-protein strain only two of the twelve 
original lines are represented in the eleventh generation; in the high-oil 
strain three lines out of twenty-four are maintained throughout the 
10-year period; and in the low-oil strain only two lines out of twelve are 
represented in the eleventh generation. 
These results are exactly what would necessarily accrue in any al- 
logamous species under continuous selection for a given character, pro- 
vided the degree of expression of that character is dependent upon a 
number of genetic factors. That several chemical characters of the corn 
grain, including protein and oil (fat), are inherited in accordance with 
Mendelian principles was determined by Pearl and Bartlett in 1911. In 
a cross between a white 
sweet corn and a yellow TasireL.—Gernnric Revations BETWEEN CERTAIN 
é rs 1 ne BRS BC 
starchy corn determina- PHYSIOLOGICAL CHARACTERS OF THE CorN GRAIN. 
tions were made by direct Character | Dominant | Recessive 
analysis of the percentage ———— ~ = 
content of the grains of Mboisture........... High Low 
the pure parent races and Nitrogen and protein Low — High 
the F, and F, progeny in Crude fat...........| Low (incomplete High 
: : dominance) 
respect to nine chemical yy peed Elian 
constituents. These are Crude fiber.........| Low High 
listed in Table L, which Pentosans.......... Low (incomplete | High 
also indicates the dominant dominance) | _ 
and recessive conditions of DUCTOSCr anes poeeseny Low (incomplete High 
these characters in the ee 
: vce Dextrose........... Low High 
cross studied. Starch............. High Low 
This evidence, although 
worked out quite independ- 
ently, supplements Surface’s analysis of the Hlinois data in a remark- 
able way. Although there are technical obstacles to a clear cut de- 
termination of the factor relations involved, yet there is no question 
whatever that these characters of high and low protein and oil are con- 
ditioned by unit factors. A priori there is no objection to assuming the 
existence of several factors which affect the percentage of protein, for 
example, and that the original ear, 121, of the superior line in the 
high protein strain represented a genotype rich in high protein factors. 
Similarly in the other strains, continual ear-to-row selection has 
gradually eliminated all genotypes except the one, two or three as 
the case may be of highest or lowest factor combinations. 
Thus we see that selection has created nothing in the course of these 
justly famous experiments; it has served merely as a means of isolating 
particular combinations of factors which condition oil and protein pro- 
duction in the corn plant. Moreover, this sorting process has not been 
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