A STATISTICAL STUDY OF SOME INDIRECT EFFECTS OF 
CERTAIN SELECTIONS IN BREEDING INDIAN CORN 
By H. I,. RiETZ, Professor of Mathematical Statistics and Statistician , and L. H. Smith, 
Chief in Plant Breeding , Illinois Agricultural Experiment Station 
INTRODUCTION 
At the Illinois Agricultural Experiment Station a considerable num¬ 
ber of experiments are being conducted in the breeding of Indian corn 
(Zea mays) by the selection of parents with respect to particular charac¬ 
ters. One of the best known of these experiments is concerned with 
selections with regard to chemical composition. This com now consists 
of four strains, known as the “high-protein,” the “low-protein,” the 
“high-oil,” and the “low-oil” strains. Other selection experiments are 
concerned with such characters as the height of ears on stalks, the number 
of ears per stalk, and the inclination of the ear on the stalk. 
The primary purpose of these experiments is to determine what 
progress, if any, can be made in regard to particular characters by selecting 
for parentsfrom year to year with respect to such characters. Itis the pur¬ 
pose of the present paper to report the results of an investigation into what 
may be called the indirect effects of some of the above-mentioned selec¬ 
tions, by a statistical investigation of the changes that have taken place 
in certain physical characters of the ears of com. The physical charac¬ 
ters treated are length, circumference, weight of ears, and the number of 
rows of kernels on the ears. A part of this work on physical characters 
of ears has been in progress on each of n generations of com. Each 
year we have either measured for each strain all the measureable ears 
produced, or a random sample of sufficient size to insure fairly small 
probable errors. To give a notion of the extent of the data used and 
of the statistical analysis, it may be stated that this analysis involves 
the preparation of 476 distinct frequency distributions. It would 
hardly be feasible to exhibit each of these frequency distributions, but 
we shall present in Table I, as a representative illustration, the 16 dis¬ 
tributions of the four chemical composition strains for the crop of 1914. 
( 105 ) 
Journal of Agricultural Research, 
Washington, D. C. 
ke 
Vol. XI, No. 4 
Oct. 22,1917 
Key No. Ill.—6 
