926 
Jour nal of Agricultural Research 
Vol. XXX, No. 10 
Table XII .—Distribution of F 2 plants for the characters rough awn , intermediate- 
smooth awn, and smooth awn, on the basis of breeding behavior in F s ; cross 
SvanhalsXLion, 1922 
F 2 class 
Distribution on basis of F 3 
behavior 
Total 
Rough 
awn 
Inter¬ 
mediate- 
smooth 
awn 
Smooth 
awn 
Rough awn___ 
Per cent 
100 
18. 9 
5.9 
908 
961 
948 
Per cent 
Per cent 
Per cent 
100 
100 
100 
1.259 
1.260 
1,264 
X 2 =l. 33. 
P =0.5278. 
Intermediate-smooth awn__ .. 
81.1 
23. 5 
251 
228 
237 
Smooth awn___ 
70.6 
100 
71 
79 
Observed frequency__ 
Corrected frequency_ ___ _ 
Calculated frequency on 12:3:1 basis. 
of other factors affecting the distri¬ 
bution of teeth on the awn. On 
account of the difficulty encountered 
in an attempt to analyze characters 
of this nature, a more careful study 
than the one made is not considered 
feasible at the present time. When all 
of the linkage groups have been iden¬ 
tified, it should be possible to locate 
easily these minor factors for dentition 
of the awn. 
Date of heading. 5 —A study was 
made of the date of heading in 135 F 3 
families of the cross SvanhalsXLion. 
The date of heading for Lion averaged 
about June 21 while that for Svanhals 
was around July 6 , a difference of 15 
days. (See Table XXVI, Appendix.) 
The F 3 lines proved to be of three kinds, 
as shown by the distribution for date 
of heading, two with a unimodal dis¬ 
tribution and one with a bimodal. 
One type was like Svanhals, one like 
Lion, while the third produced both 
early and late plants with a prepon¬ 
derance of plants heading early. These 
three types appeared in approximately 
a 1 : 2:1 ratio. (Tables XIII and 
XXVI. The last named is in the 
Appendix.) The results show a one- 
factor difference for date of heading 
between Lion and Svanhals, early 
heading tending to be the dominant 
character. 
Reaction to helminthosporium 
sativum. —As already mentioned, 
Svanhals is highly resistant and Lion 
very susceptible to the spot blotch 
disease. For a study of the inheritance 
of the reactions to this disease, F 3 lines 
from the cross SvanhalsXLion were 
used. Seventy lines from plants 
classed as 6 -rowed in F 2 and 65 lines 
Table XIII .—Distribution of F 3 fami¬ 
lies for date of heading; cross Svan¬ 
halsXLion, 1923 
Early 
Segre¬ 
gating 
Late 
Total 
33 
71 
30 
134 observed. 
33. 5 
67 
33.5 
134 calculated on 1:2:1 basis. 
X 2 =less than 1 . P=good fit. 
from plants classed as 2 -rowed were 
grown in F 3 , making 135 lines in all. 
Among these lines the characters black 
and white, as well as rough awn and 
smooth awn, were represented. 
Twenty-five seeds of each line were 
planted in a 5-foot row and two 
systematically distributed rows were 
grown of each F 3 line. The parent 
varities were planted every tenth row. 
Inoculum was prepared by culturing the 
pathogene on a cooked wheat and 
barley mixture. It was sown in the 
rows at planting, and at heading time 
the plants were sprayed several times 
with a water suspension of spores. 
Notes were taken on the infection by 
the same method as was used in previ¬ 
ous studies at the Minnesota station 
(10). By this method a numerical 
figure is obtained which is an index of 
the reaction of the line, the higher the 
figure the more resistant the line, and 
vice versa. The notes were taken on 
the lines in the replicate rows without 
knowing what figure had been given 
them in the first series. The numeri¬ 
cal figures for series one and series 
two were then correlated (Table XIV). 
The value of r was found to be 
+ 0.382 ±0.050. 
6 The time of awn emergency is taken as the most convenient criterion of date of heading. 
