May is, 1925 Inheritance of Botanical Characters in Barley 931 
reason, resistance and susceptibility 
can not be considered as absolute 
characters, and it is impossible from the 
data obtained on an F 3 line to conclude 
whether or not the line is homozygous 
for resistance. The relation of resist¬ 
ance and susceptibility to other char¬ 
acters can be studied only by consid¬ 
ering these groups in a comparative 
manner. 
Keeping in mind that the factors for 
resistance to Helminthosporium went 
into the cross Svanhals X Lion with 
the factors for rough awn and white 
glumes, it is interesting to note that 
the white-glumed F 3 lines tend to 
be more resistant than the black lines 
and the rough-awned lines more re¬ 
sistant than the smooth-awned lines. 
(Fig. 1 and Tables XXIII and XXIV.) 
Table XXIII.— Relation of resistance 
and susceptibility to other character¬ 
istics in F z families of the cross 
Svanhals X Lion 
Distri- I Average Helminthos- 
bution I porium figure 
of F 3 
families 
of— 
! 
12 | 15 
18 
21 
24 
27 
Total 
Average 
2-rowed 
| 
---! 3 
9 
10 
3 
1 
26 
19.8±0.4 
6-rowed - _ 
5 | 24 
23 
12 
2 
... 
66 
17. 2±0.2 
Black_ 
2 j 8 
9 
4 
2 
25 
17. 5±0. 4 
White..-. 
... 4 
11 
18 
6 
39 
20. 0±0. 3 
Rough_ 
2 1 4 
2 
11 
3 
1 
23 
19. 6±0. 5 
Smooth 
._-i 6 
11 
6 
23 
18.0±0.3 
The character pairs black versus 
white, 2-rowed versus 6-rowed, and 
rough awn versus smooth awn, were 
shown to be independent. Since re¬ 
sistance and susceptibility tend to be 
correlated with each of these three 
character pairs, it may be inferred that 
the chromosomes which carry the 
factors for the characters mentioned 
also carry factors for resistance and 
susceptibility’ to the spot blotch dis¬ 
ease. Thus it may be said that at 
least three genetic factors are con¬ 
cerned in producing resistance of the 
type possessed by Svanhals. That 
resistance and susceptibility are due 
to definite genetic factors is shown by 
the fact that either may be combined 
with black or white, 2-rowed or 6- 
rowed, and rough or smooth. 
Table XXV.— Comparison of the Hel¬ 
minthosporium figure for the 6-rowed 
and 2-rowed F 3 lines in regard to the 
characters early and late 
Average Helmintho- 
sporium figure 
To¬ 
tal 
Average 
figure for 
lines 
12 
15 
18 
21 
24 
27 
6-rowed early 
3 
10 
7 
P 
20 
15.6±0.3 
6-rowed late.' 
2 
Tj 
~r 
10 
20. 7dh . 3 
6-rowed se¬ 
gregating..! 
2 
11 
15 
5 . 
1 
... 
34 
17. 3± .3 
2-rowed early 
2-rowed late. 1 
4 
4 
18.0 
1 
4 
2 
i 
8 
22.4±0.8 
2-rowed se- j 
gregating..: 
2 
5 
4 
1 
12 
19. 0± . 5 
Table XXIV.—• The distribution of rough-awn and smooth-awn Fz families in 
regard to Helminthosporium figure as influenced by other characters 
