Emerson: Pistillate Flowered Maize Plants Als 
is involved, only one-third should do 
so. Of 17 F, normals tested, 5 bred 
true and 12 broke up. This is certainly 
nearer the expectation for a single fac- 
tor pair than for two pairs, but the 
numbers are too small to allow a defi- 
nite decision. The F, lots not breed- 
ing true consisted of 745 normal and 78 
tassel-seed plants. This is a deviation 
from a 3 : 1 ratio of 127.8 + 84 and 
from a 15: 1 ratio-of: 275" s—- 4:7. 
While the observed numbers fit a 15 : 1 
ratio much more closely than a 3 : 1 
ratio, the fit is too poor to be due to 
chance alone. Moreover, if the F, re- 
lation were really 15 : 1, in F, some 
3: 1 as well as 15 : 1 ratios should 
have appeared, but none of these F, 
ratios were smaller than 6 : 1, and only 
3 of the 17 were smaller than 10 : 1. 
A bit of evidence favoring the as- 
sumption of two factor pairs differen- 
tiating tassel ear from normal is af- 
forded by back crosses of F,’s with the 
recessive tassel seed. Four such back 
crosses gave 121 normal and 49 tassel 
ear. A 3:1 relation is expected from 
such crosses if two factor pairs are 
involved. The deviation from the 3 : 1 
ratio is 6.5 + 3.8, not a very bad fit. 
Another back cross, in which the F, 
plant was not closely related to those 
concerned in the back crosses noted 
above, gave 53 normal and 43 tassel 
ear, a deviation from equality of 5 + 
3.3. On the basis of the two-factor 
hypothesis, some normal plants are ex- 
pected to have one of the two reces- 
sive pairs. Such normals when crossed 
to tassel ear should, of course, give a 
3:1 ratio in F, anda 1 :1 ratio from 
a back cross. 
While the facts given above are fa- 
vorable in part to the idea that tassel 
ear is differentiated from some normal 
types by two factor pairs, itself being 
a double recessive, the evidence is far 
from convincing. The writer is much 
inclined to think that there is another 
way of accounting for the deficiency of 
tassel-ear plants below the 25% ex- 
pected on ‘the basis of a single factor 
pair. Tassel ear is at best a small, weak 
type. In this respect it is not greatly 
different from “dwarf,” a form de- 
scribed by the writer some years ago. 
Under ordinary field conditions, dwart 
plants almost never appear in numbers 
approaching those theoretically ex- 
pected. It has been possible, however, 
by germinating F, and back cross seeds 
in seed pans in the greenhouse, to show 
that dwarf is a simple Mendelian re- 
cessive. Carefully germinated seeds 
grown in large numbers have given al- 
most exactly the expected percentage 
of dwarfs. Dwarfs are apparently 
often unable to germinate under field 
conditions or die soon after germina- 
tion. This is so well known that 
progenies expected to contain dwarfs 
are almost always started in the green- 
house and later transplanted to the 
field. 
It is not known as yet whether tassel 
ear behaves in this respect like dwarf, 
but, since the plants are small and 
weak, it seems probable that the de- 
ficiency seen in the field may be due to 
a failure of tassel-ear plants to survive. 
In this connection it is important to note 
that most of the records presented 
above were made from progenies grown 
under unusually adverse conditions. 
The soil in which they were grown is 
a heavy clay. Even the normal plants 
of the same families showed by no 
means a perfect stand. Previous in- 
breeding, in case of the F,’s particat- 
larly, had greatly weakened the whole 
stock. A number of F, progenies, 
grown from these weak F, normal 
plants, were even less vigorous than the 
F,’s. Out of 15 such F, lots, involving 
486 plants, in only three lots did any 
tassel-ear plants appear, and here they 
numbered only 6 as against 80 normals. 
In two F., families, coming from a cross 
of tassel ear with a strong and quite 
unrelated normal stock, there appeared 
44 normal and 13 tassel-ear plants, 
very nearly a 3 : 1 relation. Now the 
field notes show that these lots were 
the most vigorous of all those grown 
that season. It seems likely, therefore, 
that observed deficiencies of tassel ear 
are to be explained just as similar de- 
ficiencies of dwarf are, but this cannot 
