president's address. 
9 
straw. They evince no sign of vitality until the following spring. 
When they do germinate this curious fact occurs, viz., that they 
are incapable of infecting a Wheat plant, but on a Barberry leaf 
give rise to the beautiful yellow cluster-cups with which it began. 
All these phenomena are so well known, and are detailed in all 
modern botanical works with such accuracy, that it may seem 
superfluous to enumerate them, but this has been done because 
I know how easily some of these little details are apt to escape 
one’s memory. 
Let us now pursue the subject a trifle further. IIow is it to be 
accounted for that we find crops seriously damaged in districts from 
which the Barberry is either absent or very rare ? Some years ago, 
I read a paper on Wheat Mildew, at Norwich, before the Chamber 
of Agriculture. After the meeting, Mr. W. C. Little of Stags Holt 
mentioned in the course of conversation that on the Mahonias in 
his garden a cluster-cup was very common upon the immature 
berries. He was kind enough to send me sufficient specimens of 
these disease berries for experiment, and it was found that the 
Mahonia spores were capable of producing the rust on Wheat plant 
just as the Barberry spores do. This observation was subsequently 
confirmed by Buchenau in Germany and by De Barv himself. 
Now this is an important fact, because although the Barberry is 
rare in many districts, yet the Mahonia is grown in almost every 
garden. It is moreover very frequently planted in woods as cover 
for game. The cluster-cups do not occur on the Mahonia leaves, 
but on the berries while they are still green, and before they have 
assumed the dark purple tint of maturity. As the cluster-cup is 
the starting-point of the disease — the rust being the disseminating 
form — we have now no difficulty in accounting for numerous centres 
from which the mildew may originate in this country. There is a 
further point worth considering. How is it that the fungus spore 
is able to alight on the berry ? At the time the berry receives the 
infection it is a very small object as compared to the surface area of 
the foliage. This is a question which has never properly been 
worked out, and its solution would fill up an hiatus in our know- 
ledge of the life history of these hetercecious parasites. It would 
