333 



TABLE L. GENETIC RELATIONS BETWEEN CERTAIN 

 PHYSIOLOGICAL CHARACTERS OP THE CORN GRAIN. 



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 

 starchy corn determina- 

 tions were made by direct 

 analysis of the percentage 

 content of the grains of 

 the pure parent races and 

 the FI and Ft progeny in 

 respect to nine chemical 

 constituents. These are 

 listed in Table L, which 

 also indicates the dominant 

 and recessive conditions of 

 these characters in the 

 cross studied. 



This evidence, although 

 worked out quite independ- 

 ently, supplements Surface's analysis of the Illinois 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 



