1898 | RESEARCH INTO GRAIN RUST 31 
—and the small propagation of black rust by external infec- 
tion, mentioned above, is not at all affected by the interven- 
tion of the barberry. 
2. The propagation of rust is often slight (a) between species of 
Graminee capable of bearing the same specialized form,.(b) to and 
from the ecidium host (where there is one), and sometimes (c) between 
different cultivated varieties of the same cereal. 
By reference to the table we observe that the form of black 
rust first mentioned, called f, sp. secalis, may occur on rye and 
barley, as well as on 77iticum repens, and several other grasses. 
In middle and southern Sweden 7. repens is more often and 
abundantly attacked by black rust than any other grass. It 
would be natural to suppose that if the several Graminez named 
’ grew in the vicinity of one another and one should be attacked 
the infection would ordinarly spread to the others. If so, rye 
and barley ought to be frequently attacked by black rust. Such, 
however, is not the case. Barley is comparatively little affected 
by this form of rust, and rye does not suffer from it to any great 
degree. 
It has been observed, furthermore, that barley growing near 
Triticum repens covered with black rust has remained clean week 
after week, although the weather had been very favorable for 
the propagation of the disease. We may incidentally allude to 
other observations in which the propagation of the disease from 
rusted stalks to the zcidium host, or contrarily from this plant 
to susceptible Graminez has been much less than we expected. 
But, also, propagation of rust has very often appeared to be 
small between different cultivated forms of the same kind of 
cereal, and even between different individuals of the same 
grass. There is, indeed, scarcely an agriculturist who has not: 
sometimes observed that different varieties of wheat are very 
differently attacked by yellow rust. One variety may be almost 
clean, while another is entirely destroyed. Such a case which was 
particularly noted may be here related. Inthe summer of 1894 
a variety of winter wheat (Horsford’s pearl wheat), very sus- 
ceptible to yellow rust, was cultivated at the Experiment Station 
