Dec. 22 ,1923 
Cytology of Wheat Stem Rust 
579 
distance farther on, the plastids, though larger, are below normal. By 
the fourteenth day (14a), on the contrary, there is a partial recovery in 
size and there is no longer any zone of tissue with markedly decreased 
plastids. In fact, the plastids are now of about the same size throughout. 
The area between two neighboring uredinia (Table I), where the in¬ 
fluence of the fungus is felt from both sides, does not show the extreme 
reduction in plastid size at any stage in development, so far as observed. 
KANRED AND PUCCINIA GRAMINIS TRITICI FORMS III AND XIX 
MACROSCOPIC OBSERVATIONS 
On Kanred, form III of Puccinia graminis tritici Erikss. and Henn. 
produces the 3 type of infection. It produces uredinia but, while there 
are no marked signs of uncongeniality, the growth is somewhat less 
vigorous than on Baart. 
MICROSCOPIC OBSERVATIONS 
Entrance Phenomena of Forms III and XIX 
In an earlier study (2) of Kanred inoculated with forms I and XXI 
(then referred to as the Berkeley rust), from which it is immune, it was 
found that this variety excluded a large percentage of the fungi. Appres- 
soria form on the stomata but many do not enter. A natural question 
in connection with the partial exclusion of the fungus by Kanred is 
whether congeniality or uncongeniality of the rust affects the entrance. 
A preliminary study of form III, which produces spores freely on Kanred* 
indicated that it, too, fails to enter Kanred in the majority of cases. 
Further data have been taken on this point. One lot of seedlings was 
grown in July, 1921. In material fixed four days after inoculation, 9 
fungi out of 82 had entered, or 11 per cent. An attempt was made to 
count some of this material fixed seven days after inoculation, but it 
was not satisfactory, as the weather had been exceptionally warm, and 
under greenhouse conditions the appressoria which did not enter withered 
quickly and some had fallen from the leaf. 
In order to compare the two rusts on Kanred and eliminate as far as 
possible any differences that might be due to environment, a pot of 
Kanred seedlings was inoculated with form III and another at the same 
time (the latter part of April, 1922) with form XIX. These were given 
parallel treatment throughout. Material of each was fixed two, four, and 
six days after inoculation. The results are presented in Table II. 
Table II.— A comparison of forms III and XIX grown on Kanred, showing the per¬ 
centages that have entered the host at different dates after inoculation 
Days after inocu¬ 
lation. 
Form III, rust grade 3. 
Form XIX, rust grade 0. 
Number of— 
Percentage 
of entries. 
Number of— 
Percentage 
of entries. 
Fungi. 
Entries. 
Fungi. 
Entries. 
2. 
60 
3 
5 
209 
2 3 
II 
4 . 
128 
22 
17 
200 
36 
18 
6. 
193 
20 
10 
108 
15 
14 
Total. 
381 
_ 
12 
517 
74 
14 
