54 British Urediiiece and Ustilaginecs. 



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 y^cidiuni 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 (18 16) 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 ; 



