12 
Research Bulletin No. 2 
yellows as described above, but it is also possible that action of 
a hitherto unobserved intensity factor is responsible for the 
phenomenon. 
East and Hayes (1911) reported one other case of this kind 
where dominance is comparatively complete. Two varieties of 
maize breeding true to that form of red pericarp which comes 
to complete development only in sunlight were crossed. The F 2 
generation, instead of breeding true to this color as was expected, 
gave a fraternity composed of ears with and without the red 
pericarp in the ratio of 15:1. The extracted recessives bred 
true, but no further observations were made on the segregates 
having red ears. It can hardly be doubted, nevertheless, that 
here again were two factors producing apparently the same 
visible character, each segregating from its own absence and not 
allelomorphic to each other. 
Let us now consider what peculiarities such a scheme of in- 
heritance presents as a whole. If there is absolute dominance 
and each dominant unit factor affects the zygote as fully as all 
do when combined, it would take bur a few character pairs to 
present the appearance of breeding true in F.. This Ave saw to 
be the case in the wheats. The F L , generation of 381 plants 
appeared to show no segregation. Ordinarily six pure recessives 
might be expected from this number of plants when dealing with 
three interacting factors in a heterozygous condition, but if four 
units A^A^A^A^ were crossed with their absence a r a 2 a a 4 , only one 
pure recessive could reasonably be expected out of 2^r> P 2 zygotes 
and in the numbers generally reported from pedigree cultures 
they would often be lacking. This sort of occurrence may ex 
plain the classical (for some unknown reason, because uncor- 
roborated) strawberry crosses of Millardet (1894) where the F x 
generation is supposed to have resembled the male parent and 
bred true. A striking character in the male parent rlue to four 
or five allelomorphic pairs showing perfect dominance would 
appear to give such a result. One should be careful, at least, 
about reporting heterozygotes as breeding true without sufficient 
evidence. 
Another important class of facts resting on this theoretical 
basis may be illustrated by the case of the red pericarps in maize 
that has just been described. Two maize varieties, both breed- 
ing true for this peculiar- pericarp red that develops only in a 
certain amount of light, were crossed. The F x plants, when 
selfed, unexpectedly gave one plant with colorless pericarp on 
the ears out of every sixteen. Now one of these varieties had 
been crossed previously with a white variety and had given the 
usual monohybrid ratio of 3 : 1 in F 2 . This character was 
