LINDSTROM, GENETICAL RESEARCH WITH MAIZE 345 
the p”” gene. The mutated red ear or kernel P” p""° then acts exactly 
as if it were a hybrid of ordinary red and white pericarp. 
Another striking phase of the problem occurs when a type heterozy- 
gous for the two types of variegation P"” PU mutates. In this case the 
_ gene P™” is the one affected by the mutation altho PY is known to ha- 
ve mutated in other material. The red mutation, P’” P! then behaves 
as an F, between P' Pr" x Pl’ pk, 
In addition to this interesting and well proven contribution to the 
mutation concept, Emerson has shown that another, but similar, type 
of variegation behaves in a different manner. This type, called dark- 
crown variegation, is equally as distinct in appearance as the others. In 
this case the glumes of the cob show the mutation area on the ear very 
distinctly. The surprising feature of the-dark-crown variation is that it 
is not inherited in any manner whatsoever. 
Histological examination indicates that the mutation from varie- 
gated to red (dark-crowned, red seeds) has occurred only in epidermal 
tissue, while the mutation from variegated to solid red has struck the 
underlying tissue which permitted the change to take place in the germ 
plasm. It seems entirely possible that both types of variation are fun- 
damentally the same, both being true gene mutations. 
Hayes (1917) reports an analogous case of variegation and mutation 
involving a similar but distinctly different pericarp variegation which 
he terms , mosaic’. The interrelations between ,,mosaic’’ variegation 
and Emerson’s variegated „calico” type have not yet been established. 
Emerson (1920) has presented another interesting and critical case 
of mutation which apparently involves a chromosomal disturbance, ve- 
ry likely one of non-disjunction. The situation involves certain aber- 
rant seeds in which aleurone color and endosperm characters (sugary, 
waxy and shrunken) show a distinct spotting instead of being fully co- 
lored and starchy. 
In cases where an aleurone factor and an endosperm factor are linked 
(such as C-Wx) crosses, in which recessive aleurone and recessive en- 
dosperm (waxy) are contributed by the female parent and the corres- 
ponding dominant characters by the male, the few aberrant seeds show 
a critical phenomenon of spotting or mottling. In these aberrant seeds 
— the normal condition of which is colored and starchy — the colorless 
spots of the recessive (maternal) aleurone color are in the great majori- 
ty of cases directlly underlaid by the recessive (maternal) type of en- 
