54 British Uvredinee and Ustilaginee. 
in May, 1816, in a rye-field, three small barberries ; one of 
them did not thrive, but the other two developed nineteen 
leaves before the end of May, nearly all of which had the 
yellow spots (of Acidium berberidis) upon them. When, 
in the middle of the following June, the rye immediately 
surrounding these two bushes became rusty, I invited, by 
a notice in the newspapers, every one interested in the 
question to come and convince themselves of the pernicious 
influence which the barberry exerts. On account of this 
invitation many people came to visit me, and all of them, 
the learned as well as the unlearned, declared that they 
could accept no other cause for the rust on the rye than 
_ the small barberry plants.. They were astonished that so 
small a cause should have produced so great an effect. On 
June 22, most of the rye plants for thirty to forty feet 
(square feet) around these small barberries were more or 
less rusty, mostly so to the north and north-west, but for a 
long time afterwards not even a single rust spot could be 
found elsewhere in the field.” 
In the same year (1816) Schoeler performed the follow- 
ing experiment :—Some fresh branches of the barberry 
bush having rusty leaves upon them were cut off, put into 
a box, and carried to a rye-field, where the rye was still 
moist with dew. The rusty barberry leaves were applied 
to some of the rye plants—to the straw as well as to the 
leaves—by rubbing them with the underside of the affected 
barberry leaves, until he could see some of the “yellow dust” 
(spores) of the fungus adhered to the rye plants. The 
infected rye plants were then marked by tying them to 
sticks driven into the ground. In five days’ time these 
plants were badly affected with rust, “while at the same 
time,” says Schoeler, “not one rusty plant could be found 
anywhere else in the whole rye-field.” 
The question, however, was not even now fully decided ; 
