180 BOTANICAL GAZETTE [SEPTEMBER 
grain fields, and might easily be accounted for by the change of 
host species if the heteroecism of the fungus is only facultative. 
A suspicion has frequently been expressed that the black rust 
spreads to the grain fields by aid of the grasses which either harbor 
the mycelium over winter or are infected early by aecidiospores. 
In order to determine the interval between the appearance of rust 
on grasses and cereals, the following observations were made in the 
spring of 1905. Rust the following summer, although not as abun- 
dant in North Dakota as in 1904, was still quite pronounced. 
TABLE IV 
FIRST APPEARANCE OF Puccinia graminis Pers. UPON GRASSES AND CEREALS AT 
Farco, NortH DAKOTA, IN THE SPRING OF 1905 
dh Host species nate Location Remarks 
June 27. .' Hord. jub. Uredo Grass garden A few pustules on a single 
plant 
June 29..| Hord. jub. Uredo Near barberry 
July 6...) Spring wheat | Uredo . | Field Far removed from barberry 
July g....| Agr. rep. Uredo Near barberry | Present in abundance on 
: both Agr. ii = Hord. 
jub. Non d else- 
whee although. a diligent 
sear — made. 
July to...) Winter wheat*} Uredo Field Found i sh oi a at a 
. considerable distance 
from bar ushes. 
July 12...| Agr. rep. Teleuto | Near barberry Present on both Agr. rep. 
and Hord. jub. 
July 13...| Winter wheat | Teleuto Field Same ‘lot of winter wheat 
mentioned above. 
July 16 ..| Spring wheat | Uredo Field Ascoicine quite generally 
on all the oldest wheat. 
| 
* This was an experimental ge of winter wheat in charge of Dox n J. H. ie the agro 
mist, and the writer was not aware of its presence until July 10, when the plants which had avn 
the winter were thoroughly cov: er with mature uredo pustules of P. graminis, some Fadie old, the rust 
having first appeared probably ro—r4 days earlier. 
The foregoing table shows that P. graminis probably appeared 
upon the experimental plot of winter wheat almost or quite as 
early as upon Agropyron repens and Hordeum jubatum, even when 
the latter were in the immediate vicinity of the barberry. It 
also shows that, with the exception of the one case mentioned 
