74 The Journal 
be determined until seed-pan germina- 
tion is tried out. 
TASSEL SEED AND TASSEL EAR AS 
GENETICALLY DISTINCT TYPES 
It was stated early in this account 
that tassel seed and tassel ear were at 
first supposed to be identical, but that 
they are now known to be distinct 
types. The only evidence so far given 
in support of this statement, however, 
is the fact that the terminal inflo- 
rescence of tassel seed is a loose pan- 
icle, while that of tassel ear is more 
compact, both the central spike and the 
branches being ear-like in appearance. 
It remains to be shown that these two 
abnormalities are genetically distinct. 
Crosses of Tassel Seed with Tassel 
Ear.—If tassel seed and tassel ear were 
fundamentally identical, differing only 
in density of the inflorescence, vigor of 
growth, and the like, somewhat as 
strains of normal corn differ, crosses 
between the two should give pistillate 
flowered plants. Of course it is im- 
possible to cross two wholly pistillate 
flowered types directly, but no mere 
fact of this kind need bother us long. 
Conclusive evidence can be obtained 
from crosses of normal plants, the one 
heterozygous for tassel seed and the 
other for tassel ear. Or, better still, 
a plant heterozygous for one recessive 
type may be crossed with the other 
recessive. 
If the two recessive types were the 
same, the cross of two heterozygotes 
should give 25% of pistillate flowered 
plants in the progeny. Or, on the same 
assumption, if an F, plant heterozygous 
for tassel seed is crossed on to a tassel 
ear and a plant heterozygous for tassel 
ear is crossed on to a tassel seed, 50% 
of the progeny should be pistillate flow- 
ered. All these crosses have been made 
and progenies grown. The cross of the 
two heterozygotes yielded 69 normal 
plants. A normal plant heterozygous 
for tassel seed crossed on to a tassel ear 
gave 40 normals, and a normal plant 
heterozygous for tassel ear crossed on 
to a tassel seed resulted in 33 normals. 
Not a single pistillate flowered plant 
of Heredity 
appeared among the 142 normals. This 
is regarded as conclusive evidence es- 
tablishing the genetic distinctness of the 
two pistillate flowered types. What the 
double recessive will be like cannot be 
told until another generation is grown. 
Distinct Linkage Relations of Tassel 
Seed and Tassel Ear.—The story of the 
linkage relations of tassel seed and tas- 
sel ear is only partly known, but suffi- 
cient information is at hand to prove 
that the two abnormalities show dis- 
tinetly different linkage relations with 
certain other factors of the maize plant. 
A back cross involving tassel seed, 
Ts ts, and a factor pair for pericarp 
color, P p, gave 81 normal plants all 
with red pericarp and 77 tassel-seed 
plants all with colorless pericarp. The 
pair Ts ts is, therefore, very closely 
linked with P p or the two pairs are 
identical. In a similar back cross in- 
volving P p and tassel ear, Te te, there 
appeared normals with red and with 
colorless pericarp and tassel ears with 
red and with colorless pericarp. There 
were 50 plants of the parental combina- 
tions and 56 of the other two combina- 
tions of the two characters in question. 
This is a “crossover” percentage of 
52.8, or a deviation from 50 of 2.8 + 
3.3. Apparently, therefore, tassel ear 
is not linked with pericarp color. Cer- 
tainly it does not show the same linkage 
as tassel seed. 
It has long been known that a re- 
cessive leaf abnormality called ligule- 
less Lg, lg, is linked with a dominant 
plant color called sun red, in which the 
factor pair B b is involved. The cross- 
over percentage commonly observed is 
about 30. A back cross involving B b, 
Lg lg, and tassel ear, Te te, produced 
96 plants with all but one of the eight 
possible combinations of these three fac- 
tor pairs. The crossover percentage for 
B b and Lg lg was 29.2, for B b and 
Te te 20.8, and for Lg lg and Te te 
45.8. The crossover percentage for 
liguleless tassel ear is so near 50, devia- 
tion 4.2 + 3.4, that, standing alone, 
it affords no satisfactory evidence of 
linkage. There can be little doubt, on 
the other hand, that B b and Te te’ are 
