CORN BREEDING 
facts are of special interest in corn because of their relation to the 
inheritance of certain kernel characters, as will be shown later. 2 
RELATION BETWEEN REPRODUCTION AND INHERITANCE 
The new plant develops from the single cell that was formed by the 
fusion of the egg with a sperm, and this is its only connection with the 
preceding generation. 
The endosperm supplies the food necessary for the young plant 
until it has become established in the soil. It has no influence on the 
character of the new plant other than that exerted as a food source. 
The hereditary characteristics of the plant therefore must be deter- 
mined by what it receives from the egg and the sperm, among which 
are the chromosomes. 
Throughout this account emphasis has been placed upon the 
manner in which the chromosomes divide. The facts given are based 
upon actual observation and are of the utmost 
importance because, in connection with the ob- (f^ ~~~p^~~ ==s %Z P 
served method of inheritance of many differ- I / A \ / A 
ent characters, they point clearly to the chro- 11 //A\\ * If S 
mosomes as constituting the mechanism of 
heredity. 
Fig. 2. — Diagram of a 
section through a 
kernel of corn show- 
ing the different 
parts : P, Pericarp ; 
A, aleurone layer of 
the endosperm ; S, 
starchy endosperm ; 
E, embryo ; G, scutel- 
lum. Only the peri- 
carp (P) is formed 
exclusively from ma- 
ternal tissue, the 
other parts resulting 
from the union of a 
sperm with either 
the egg or the polar 
nuclei 
THEORY OF INHERITANCE IN CORN 
A cross between two unlike varieties of corn 
produces plants in the first generation that re- 
semble one or the other parent with respect to 
certain dominant characters, whereas in other 
characters the plants are intermediate, showing 
a blending of the parent types. The second 
generation of such a cross has a much wider 
range of variation than the first, and the char- 
acters of the parents tend to appear in all pos- 
sible combinations. There is a marked difference, 
however, in the way that characters behave in 
transmission. 
The present theory of inheritance is based 
upon the fundamental concept that the form 
and functioning of the individual is governed by definite units or 
factors that descend through the generations practically without 
change and which produce the infinite variation found in plants and 
animals through unlimited recombination. Some characters are 
differentiated by one factor, others by two or more. 
There is good evidence that occasionally a factor may change or 
mutate. This is of much importance from its evolutionary signifi- 
cance but may be disregarded as relatively unimportant in its rela- 
tion to practical corn breeding. 
In general, both the sperm and the egg carry a full set of the 
inheritance factors characteristic of corn. Consequently, the ferti- 
lized egg cell and the cells of the plant formed from it contain a double 
set of such factors. The behavior of these factors in inheritance 
may be followed more readily in a typical example. 
2 Among the reports on fertilization, kernel development, and the chromosome condition 
in corn may be mentioned 50, 56, 58, 61, 75, 76, 77. 
