990 
Journal of Agricultural Research 
Vol. XXIV, No, 13 
The range of infection for Mindum was considered to include o and i 
types of infection. In the immune class, 236 of the 248 plants had o type 
infections, hence the immunity of Mindum to Form I is evident. The 
pots of Mindum were classified as 20 immune, 2 near-immune, and i 
heterozygous (PI. 2). 
In the 23 control pots of Pentad 167 plants were infected. Of these, 
147 had types of infection ranging from x— to 4, and 20 showed types 
o and I. Leaving these 20 plants out of consideration, the range of the 
type of infection was from x— to 4, as was the case wi^ Kubanka No. 8 
when inoculated with Form XXXIV. At first glance it would seem that 
20 is a rather large number of plants to leave out of consideration in a 
population of 167. It is not as significant as it appears to be, however, for 
many of the plants with o type infections showed only a few vague 
necrotic flecks which were not clearly distinguishable from similar effects 
sometimes produced on seedlings as a result of environmental conditions. 
The classification of Pentad pots gave 16 as susceptible, 3 near-susceptible, 
and 4 heterozygous (PI. 2). 
A total of 166 Fg families were tested. The number of Fg plants inocu¬ 
lated was 2,340. Of these 2,169 showed infection. The distribution of 
Fg plants according to their types of infection and to the classes of the 
various families to which they belonged is given in Table V. The 166 
Fg families were classified as 44 immune, 13 near-immune, 82 heterozy¬ 
gous, 10 near-susceptible, and 17 susceptible (PI. 2). 
A larger proportion of families was classified as immune and near- 
immune than as susceptible and near-susceptible. This was to be ex¬ 
pected from the progeny of the parents, one of which was immune and 
the other only moderately susceptible. Approximately one-eighth of the 
pots of Mindum, the immune parent, fell outside the immune class. The 
Fg progeny, considered on this basis, shows 44 plus 5.5, or a total of 49.5 
families which appeared to be as immune as the immune parent. The 
r.atio of 49.5 to 166, which is the total number of families classified, 
would seem to indicate the presence of a single differential factor. The 
variable results obtained with the Pentad parent prevent a more detailed 
analysis. 
The distribution of plants in the heterozygous class with respect to the 
various types of infection shows a total of 734 with o, i, and 2 types of 
infection (723 being of the o type) and 288 with types ranging from x — 
to 4, The dominance of immunity is evident. 
RKSUnTS OF INOCULATIONS OF MINDUM X PI^NTAD Fg FAMILIES WITH 
BIOLOGIC FORM XXXIV 
The results obtained are summarized in Table VI. Thirty-three con¬ 
trol pots of each of the parental varieties were inoculated. The reactions 
of Mindum and Pentad to Form 34 were the reciprocals of their reactions 
to Form I. Of the 375 Mindum plants that showed infection all but 9 
had x-1- and 4 types of infection. The remaining 9 plants had x— and 
3 types of infection. Mindum is here the susceptible parent with a range 
of types of infection w'hich is narrower than that of the susceptible parents 
in the work previously discussed. The pots of Mindum were classified 
as 2 heterozygous, 4 near-susceptible, and 27 susceptible (PI. 3). 
