SUSCEPTIBILITY TO PARASITISM IN MAIZE 
297 
differences are not due to differences in local infection. Maize was 
grown on the field the previous year and smut was fairly abundant, 
so that there was probably as good an opportunity for the plants to 
become infected in one place as in another. Although smut infection 
is not considered to come from the seed in the case of maize, the possi- 
bility of this factor as a cause of the similar results in the different plots 
is ruled out because the seed for any one strain grown in the three plots 
came from different hand-pollinated plants grown the previous year. 
So that if one strain was badly affected in one plot the fact that it was 
also affected in another plot was not due to the use of the same con- 
taminated seed. The seed plants of all the different strains were 
grown in the same place in 1916 and had an equal opportunity of 
infection. 
No data were taken on the infection by smut previous to 191 7. 
It is quite likely that these strains will show variability in the extent 
to which they are infected by smut in different years, but, as shown in 
table I and summarized in table 2, out of nearly one thousand indi- 
viduals not a single plant of strain number 1-6-1-3 was affected, while 
in a nearly equal number of plants of strain number 1-7-1-1 about 
Table 3 
Susceptibility to Smut of a Non-inbred Variety of Maize, of Two Inbred Strains Derived 
from this Variety, and of the First and Second Generation Hybrids between 
These Two Inbred Strains 
Pedigree Number 
I 
I-7-I-I-I-4-7-5-4-7-I 
I-6-I-3-4-4-4-2-4-4-2 
r (1-7-1-1-1-4-7-5-4-7) X \ p 
\ (1-6-1-3-4-4-4-2-4-4) ( 
r (1-7-1-1-1-4-7-5-4-7) X 1 p 
I (1-6-1-3-4-4-4-2-4-4) / 
Number of 
Plants Grown 
114 
52 
80 
36 
97 
Number of 
Plants Afifected 
Percent of 
Plants Affected 
1.75 
5-77 
o 
5-15 
ten percent of the plants were affected. These two strains were grown 
in rows side by side in three different plots. The other two strains 
derived from this same source and the two strains from another variety 
all show a small amount of infection. Clearly there are marked dif- 
ferences in susceptibility in these strains. The differences are reason- 
ably consistent in the three different places in which the plants were 
grown and show without a doubt that segregation of susceptibility to 
