Feb. 9» 1924 
Resistance of Wheat to Puccinia graminis tritici 
397 
The plants of this series were then inoculated on April 1, 1922, with 
urediniospores of biologic Form XXXIII. This form, as shown by 
Stakman and Levine (54), produces a type “2” infection on Haynes 
Bluestem. It was hoped that a form which produced a type 2 infection 
would be more sensitive to changes of the host than a form to which 
the host is very susceptible or very resistant. The different pots of the 
same salt combinations were not placed together in the incubation 
chambers but were scattered at random so as to prevent any two pots 
with the same salt combination from being together. The plants were 
so heavily inoculated by dusting with urediniospores that the spore 
mass could be seen easily on the leaves. The cloth chambers were 
then covered with wet cheesecloth, an atomizer was inserted through 
slits along the sides near the top and a fine mist spray was forced into 
the chamber. The air remained saturated throughout the 48-hour 
incubation period, following which the plants were placed on the green¬ 
house bench for 14 days. No observations were made on the stomatal 
movements, although this would have been desirable. 
The series of June 14 was exactly like the previous one except that no 
additional salt solution was added at the time of inoculation. The 
plants were inoculated on July 19, when about 5 weeks old. They, 
therefore, were younger than those of the first series, but they were fully 
as well developed, owing to the difference in available sunlight. 
RESULTS OP INOCULATION WITH BIOLOGIC PORM XXXUI 
The degree of rust infection on the seedlings is given in Tables VIII 
and IX. 
Table VIII .—The effect of different nutrients on the growth of Haynes Bluestem wheat 
plants in sand cultures started fanuary 29 , 1922 1 and on the development of stem rust 
ccmsed by biologic Form XXXIII used as inoculum on April r, 1922 0 
Series 
No. 
Changes in basic nu¬ 
trient solution. 
Percentage of plants 
infected. 
Severity of 
infection. 
Character of growth. 
101 
None (control).... 
KN 0 3 added. 
MgHP 0 4 added .. 
K 2 S 0 4 added. 
None... 
Good. 
102 
103 
104 
85:. 
None. 
1 uredinium on 1 
Medium ... 
Medium ... 
Excessive tillering. 
Medium. 
Do. 
o"8 
H M 
NaNOg added .... 
CaHP 0 4 added... 
plant. 
7 o . 
None... 
Fair; much tillering. 
Medium. 
® These observations were made by Dr. E. C. Stakman and M. N. Levine. 
