54 Proceedings 
in July or August of conspicuous yellow blotches on the upper 
surface of the pear-leaf. When these blotches are numerous, a 
premature defoliation takes place, with the result that the 
young wood of the pear does not ‘ripen’ properly, and the 
pears themselves do not grow to their proper size. On the under 
surface of the affected leaves (whether on the tree or on the 
ground), exactly opposite the yellow blotches on the upper 
surface, the fungus forms a fructification known as ‘cluster-cups.’ 
Now the curious fact is that if spores are taken from these 
‘cluster-cups’ and placed on a pear-leaf, no infection results. 
The present fungus is one which requires ¢wo distinct plants 
to live upon in order to complete its life-history. In the present 
case the second plant is a species of Juniper, viz.: Juniperus 
Sabinae. Spores from a pear-leaf infect this species of Juniper 
and give rise there to spawn (mycelium) which lives peren- 
nially in the stem of the Juniper, breaking out from cracks in 
the stem each spring in the form of a yellow jelly-like fructi- 
fication. Spores from this stage of the fungus on Juniper, 
while unable to infect the Juniper, are able to infect pear- 
leaves, and form there ‘cluster-cups.’ I have known several 
instances in which trained pear-trees have suffered severely 
from the present fungus, and in these cases the growers,— 
though of course anxious to keep their pear-trees free of the 
disease—have been growing in some corner of their garden a 
plant or two of the particular Juniper necessary for the con- 
tinuance of the life-cycle of the pest. On this information 
being conveyed to them they have—although sometimes not 
a little incredulous of any good resulting—made short work 
with a spade of the Juniper bushes. They have seen no more 
‘pear-leaf cluster-cups.’ 
In conclusion, I should like to make the suggestion that Nat- 
ural History Societies such as ours would find a very profitable 
field for work in connection with plant-diseases, not only in 
investigating the still unknown life-histories of many of the species 
of fungi and insects which cause these diseases, but also in dissem- 
inating the scientific knowledge which has been gained in 
connection with the subject. There are many ways in which 
a Natural History Society can act. The Norwich Natural His- 
