oct. 22,1917 Indirect Effects of Selections in Breeding Indian Corn 145 
SUMMARY 
THE) FOUR STRAINS WITH RESPECT TO CHEMICAL COMPOSITION 
(1) It is found that four distinct types of corn as regards length, 
circumference, weight of ears, and number of rows of kernels on ears 
are so well established that we may assign orders of values to the means 
of these characters that persist with but few exceptions in such changes 
of environment as have been experienced in 11 years of planting, from 
1905 to 1915. 
(2) While a few slight but significant progressive changes have been 
noted, the selections for chemical composition from 1905 to 1915 have 
not changed decidedly the differences in mean values of these characters. 
In fact, we are unable to assert with any high degree of probability that 
the strains differ more or less with respect to these characters during 
the second half of the period 1905 to 1915 than during the first half. 
(3) The standard deviations of the strains do not differ nearly so 
much compared to their probable errors as do the means, and it is not 
in general nearly so easy to discriminate among strains by the differ¬ 
ences of standard deviations as by the use of means. There is one marked 
exception to this, in that we easily distinguish high-protein and high-oil 
from low-protein and low-oil strains by the differences in the standard 
deviations in weights of ears. 
(4) No progressive change of consequence has taken place in standard 
deviations. 
(5) The coefficients of variability, in comparison to their probable 
errors, differ still less in a given season than the standard deviations, 
and there is no very general tendency for the coefficients of variability 
to maintain a definite order of values. That is to say, the differences 
of coefficients of variability of the four strains seem to be fairly well 
described, with certain exceptions noted in the paper, as random 
fluctuations. 
TWO-EAR STRAINS 
(6) The upper ears have a significantly larger mean value in length, 
weight, and circumference than have the lower ears on the same stalks. 
(7) The means with respect to weight, length, and circumference of 
single ears are in each case larger than the corresponding means for the 
lower ears of the same plot. The means with respect to weight and 
circumference are also in general larger than these means for upper 
ears of the same plot. However, strange as it may appear, the mean 
lengths of single ears are on the whole less than those of upper ears. 
(8) A striking fact in the comparison of the single ears with the upper 
and lower ears is the greater standard deviation in the weight of single 
ears. 
