COKN BREEDING 19 
With these facts in mind, it is clear that a strain of corn breeding 
true for all green both in the seedling and in the mature plant is 
homozygous for the dominant members of all of these preceding 
factor pairs. More than 20 such factor pairs, the recessive of any one 
of which will cause some type of spotting or striping, have been 
studied in some detail, and several others have been recognized and 
have been shown to be hereditary. No one of these occurs to any 
I great extent in open : fertilized corn. There are so many of them, 
however, that it is difficult to find plants in open-fertilized fields 
that do not carry one or more types of spotting or striping, whereas 
in self-fertilized corn it is almost impossible. Thus, among 3,750 
ears of corn of standard Corn-Belt varieties selfed for the first time, 
532 (14.2 per cent) carried heritable chlorophyll defects that showed 
in the seedling stage {37). How much these may affect the vigor 
and consequent yield of corn is problematic. Some of the more 
extreme forms are very deleterious, resulting in early death or small 
stunted plants almost or entirely barren, and it seems logical to 
assume that the lesser ones also are detrimental. 
Before leaving this phase of the subject it is advisable to point out 
that to say that these spottings and stripings are hereditary may be 
only part of the truth. Several symptoms are produced by an unbal- 
anced soil solution that can not be differentiated from some of the 
characters that have been shown to follow hereditary lines (31). 
It therefore is probable that, in some cases at least, the condition 
inherited is a susceptibility or a resistance to these unbalanced con- 
ditions. In such cases the appearance of the symptoms is a result 
of the inherited susceptibility together with the presence of the 
environment necessary to their development. This, of course, is but 
a more complete analysis of cause and effect in these specific cases. 
It is an extremely helpful point of view, however, in properly 
weighing the importance of these abnormalities as they appear in 
favorable environments. Looked at in this way, some of them are 
but symptoms of an inherited inability to function properly rather 
than specifically inherited pattern factors. 
DWAKFXESS 
Several dwarf forms are known in corn (23, 45). One of these is 
characterized by the reduced size of all of its parts. In another 
the length of the internodes is the only part affected, resulting in 
short plants having leaves that are normal in size and number. 
Between these extremes are other forms, many of which are charac- 
terized by abnormalities other than dwarfness. 
One form that has been named " dwarf " is conditioned by the 
factor pair D d. Normal plants are D D and the dwarf plants are 
d d. The latter are characterized by their very short stalks which 
ordinarily are not more than one-fourth as high as related normal 
♦ plants. They also are characterized by other differences that need 
not be considered here. 
Another dwarfed form, called " anther ear," also is considerably 
shorter than related normal plants. This form, however, is not 
characteristically as short as is the dwarf type. Anther ear has 
been shown to be a simple recessive (an an) to normal (An An). 
