156 Transactions british Mycological Soctety. 
Again wheat inoculated with the same rust early in March and 
kept in the open developed pustules in a fortnight. 
The fact that brown rust was flourishing during the greater 
part of this period, and was never altogether absent, shows that 
climatic conditions were not unfavourable. Keeping the data 
of the incidence of this rust for the season 1920-21 and 1921-22 
in mind, one cannot help suspecting, that there is a clear con- 
nection between the incidence about autumn time and the 
origin of rust on winter crops in the following spring, as the 
following chart will show. 
Date | 1920-21 | 1921-22 
October Common Only 4 to 5 plants 
November Very common Oct. 25th. None afterwards 
December Rare No trace 
January 21st On fresh crop 
February Very common 
March Epidemic 
April s 
May ” ” ” 
June Just appearing 
It has been shown that climatic conditions during winter and 
spring (1921-22) could not be taken as a factor in accounting 
for the absence of yellow rust this year. Evidently one is forced 
to the conclusion that the source of infection for the winter 
crop lies in the uredospores occurring on self-sown plants about 
autumn time. 
Again it has been stated above that wheat sown late in the 
season (Nov. 30th, 1920) did not get rusted till March 3rd, some 
six weeks later than the crop sown Oct. 5-7th. It may be 
pointed out that by the time the seedlings could appear uredo- 
spores were very rare so that the chances of an infection at that 
time were scanty. Besides, from the 12th of December 1920 
onwards, there was an exceptionally heavy frost which lasted 
more than a week. Early in January 1921 again the uredo- 
stage was very rare. Keeping these facts in mind one can safely 
conclude that most probably the infection of the wheat plot 
under discussion was due to wind-blown uredospores, as there 
was plenty of yellow rust available by the end of January. The 
reason why this plot did not show any rust till the beginning 
of March will be clear from a study of facts discussed under 
“incubation periods.” 
As regards the seedlings transplanted outside the laboratory 
it is interesting to note that up to the middle of July (when 
the plants were quite ripe and dry) no trace of yellow rust was 
found on these plants, in all for a period of over eleven months. 
