3 12 
Journal of Agricultural Research 
Vol. XXV, No 7 
previously that the development of staminate ear spikes is dependent 
upon the interaction of two factors, the character appearing when either 
or both factors are homozygous recessive ( 8 ). In addition, one of these 
factors is associated or linked with brachytic, while the other is inde¬ 
pendent of stature. 
The percentages of this character in the three stature groups of the 
present hybrid necessitates the assumption of a third element for the 
production of staminate spikes. This third element is linked closely 
with dwarf stature. 
Such characters are generally considered as multiple factor characters 
comparable with those which come into expression only when all the 
factors are homozygous recessive. There is little to justify such a class¬ 
ification except perhaps an inability to distinguish somatic differences, 
an inability which admittedly is personal. 
With cases such as the aleurone color of the seeds, where all white 
seeds have very much the same shade, there is little hope of distinguish¬ 
ing a difference between the several factors and little is to be gained 
by considering each of the several forms of genetic whites as separate 
monohybrid characters. With other characters where distinctions are 
not made in the beginning they are often recognized later, and the varia¬ 
tions are then classified as independent monohybrid characters. 
It would seem best to consider those characters which come into expres¬ 
sion when single or when each of several factors is homozygous recessive, 
as distinct monohybrid characters, even though they can not be dis¬ 
tinguished readily; whereas those characters which appear only when 
more than one factor is homozygous recessive are true multiple factor 
characters. With the former each variation in the germ plasm results 
in a visible somatic change, while in the latter a somatic change results 
only from the cumulation of several variations in the germ plasm. 
It is obvious that a cross involving two independent monohybrid 
characters which are indistinguishable in appearance would result in the 
familiar 9:7 dihybrid ratio in the second generation, and the present 
hybrid may illustrate such a case. 
It is clear that the dwarf-brachytic hybrid is homozygous dominant 
for the factor for staminate ear spike which is linked with brachytic and 
heterozygous for a factor independent of stature. If this were all, then 
monohybrid ratios would be expected for the entire population as well 
as for each stature group, but if a second staminate ear spike character 
were involved, the gene for the latter being identical or closely linked 
with dwarf stature, the observed percentages would be approximated 
closely. 
On this hypothesis 25 per cent of the plants in both the normal and 
brachytic groups would be expected to have staminate ear spikes while 
all the plants of dwarf stature would have this character, and the per¬ 
centage for the total population would be 43.75, provided the three 
stature groups were present in the expected ratio of 9:3:4. 
If this hypothesis be true, there are then four staminate ear spike 
characters, all similar in appearance but distinct genetically. One of 
these is linked closely with dwarf stature, one is associated with the 
anther ear semidwarf of Emerson, one is linked with brachytic culms, 
and the other seems independent of stature. 
Variations such as these, strikingly similar in appearance, which prove 
to be distinct genetically when crossed, are being found with increasing 
frequency in maize. When such variations affect a similar and peculiar 
