148 Transactions British Mycological Soctety. 
the University farm on self-sown plants or regular crops in the 
spring or summer of 1921. 
(1921-22.) No black rust was found on cereals or wild grasses 
at the University farm in the autumn of Ig2r or the spring or 
summer of 1922, even up to harvest time. 
It may be pointed out that the greater portion of the plot 
under observation in the autumn of 1920 was left unploughed 
and one could see a large amount of old straw with teleutosori 
throughout the spring and summer of 1921. The new crop of 
wheat was sown on the adjacent plot. 
This total absence of black rust goes a long way to disprove 
the possibility of direct infection of graminaceous hosts by 
sporidia produced on the germination of teleutospores which 
were present in plenty on the adjacent plot. 
It is essential in this connection to state that there are no 
plants of wild barberry known to exist in the near neighbour- 
hood of the University farm. 
(b) Overwintering of the uredospores. 
It is very doubtful if fresh pustules of black rust are at all 
developed during the winter months in this locality. During 
the last two winters (1920-21, 1921-22), although comparatively 
mild, no such pustules were observed. Moreover the complete 
absence of this rust on self-sown plants of wheat which bore 
uredo-pustules of both yellow and brown rusts during the 
greater part of the cold season (1920-21) indicates that black 
rust cannot stand the cold of an English winter. Similarly 
Couch grass (perennial as it 1s), which was once covered with 
this rust in the autumn of 1920, has never shown a pustule of it 
at the University farm since that time. 
Plants of rusted Couch grass transplanted to pots in November 
and kept in the open showed no uredo-sori after two months 
and have since then been quite free from them. 
As regards the viability of the uredospores collected from the 
open in winter, it may be pointed out that inoculations tried on 
wheat in the laboratory during November and early in December 
1920 gave satisfactory results and the spores showed good ger- 
mination. By the second week of December the spores had 
practically lost their viability, and consequently it was im- 
possible to infect seedlings even in the laboratory with uredo- 
spores (old as they were) from the open after that date. 
That the loss of viability was due to the effect of cold is clear 
from the fact that since November 1920 up to July 1922 the 
writer successfully kept a culture of this rust in the laboratory. 
