Corn Investigations 
41 
all eggs and sperms produced by the offspring will have nuclei 
which carry the same Mendelian factors. This purified condi- 
tion of the germ plasm, in which all zygotes, i. e., eggs and 
sperms, are alike, is called homozygous as opposed to the hybrid 
or heterozygous condition where two unlike zygotes have united 
and where many different kinds of zygotes may be formed by 
segregation of the factors derived from the parents. 
The elemental strains differ in such visible physical and 
physiological characters as height of stalk, diameter of stalk, 
leaf area, leaf width, erectness of leaves, suckering tendency, 
brace root development, lodge resistance, firing of leaves, firing 
of tassels, sterility of tassels, barrenness of ears, stalk and leaf 
color, grain color, cob color, silk color, anther color, tassel con- 
formation, shank development, ear type, kernel type, grain yield, 
disease resistance, and earliness of maturity. 
Many heritable variations and gradations of these and 
other plant characteristics are found in innumerable hybrid 
combinations in an ordinary corn variety. The particular chance 
combination of factors or groups of factors upon fertilization of 
the egg determines the exact nature of many of the individual 
plant characters as well as of the complete assemblage of char- 
acters comprising the plant in its entirety. 
The more closely any variety, or individual corn grower’s 
subvariety, has been selected for trueness to plant or ear type, 
thru prolonged continuous selection, the fewer will be the num- 
ber of elemental strains represented in its composition. Accord- 
ingly, the greater will be the likelihood under ordinary field 
conditions of some identical factors of inheritance from both 
parents uniting in the process of fertilization. Whenever these 
identical factors represent growth or vigor or production char- 
acters in the offspring, then there is likelihood of reduction in 
the size, vigor, and production of the individual offspring so 
constituted. 
When all of the growth factors in both parents are iden- 
tical, as in an artificially reduced “pure line,” a marked degree 
of reduction in vigor, growth, and production results. Since 
there is variation in the degree of growth, vigor, or production 
represented in the corresponding Mendelian factors, much varia- 
tion occurs in the vigor and productiveness of the different dis- 
tinct elemental strains. In turn, when certain pairs of elemental 
strains are hybridized by controlled fertilization, their lines of 
immediate first generation offspring will differ from each other 
in vigor, growth, and production, in accordance with the effect 
