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munity. Preventing the access of germs from the air by spraying 
the trees with some antiseptic is theoretically possible, but the diffi- 
culties in the way of practical application are so great as to give no 
hopes of success. 
Lear Brigut AND Soap. 
Fusicladium pyrinum, Fekl. 
Leaf blight appears as dark brown or blackish spots on the leaves, 
leaf stalks and one year old branches. It is most noticeable on the 
under surface of the leaves forming indefinite patches, at first barely 
perceptible in the slightly changed color of the surface, but finally 
becoming more extended and curling the leaf, especially when on 
the midrib, by stopping its growth. . 
The amount of injury done to the pear tree is often very consid- 
erable, as it is a fungus and draws heavily upon the tree’s food sup- 
ply to maintain its own growth, and also interferes with the elabora- 
_ tion of new material by obstructing the light and weakening the 
assimilative power. The fungus inhabits the part of the leaf just 
beneath the surface with a dense growth of mycelium, from which a 
great number of vertical branches are sent up into the air bearing 
the spores. This manner of growth gives the surface a minutely 
velvety appearance to the unaided eye. 
Sometimes the fungus is seated on thickened scab-like spots on 
the under side of the leaf, varying from mere points to an eighth of 
an inch across, and occasionally coalescing into larger areas. Small 
holes are to be seen in some of the spots as if an insect had escaped. 
These raised spots are in fact caused by a minute mite, phytoptus 
piri, and the spongy growth of the leaf which it induces seems 
specially favorable to the growth of the fungus. 
The leaf blight thrives with equal vigor upon the fruit where it 
causes the disfigurement and injury known as scab or rust. Its 
effect in checking growth is seen better here than on the leaves, 
owing to the much more rapid development of the fruit, and gives 
the one sided and spotted appearance which detracts so largely from 
the marketable value. 
Our knowledge of the life history of this fungus is not very com- 
plete. The exact mode of distribution, and manner of securing a - 
foothold on the new growth of the season are almost unknown, but 
yet are important items in devising a method for its control. Pril- 
lieux,* who studied it in France, thought that it might be intro- 
duced upon young trees in the process of grafting, and could be 
perpetuated on.a tree once attacked by being carried over the winter 
on the young branches. But it is quiteas likely that the distribution 
is effected by spores blown through the air. It becomes most troub- 
lesome in rainy seasons, and for the same reason its development is 
accelerated by damp warm weather, or a damp location. 
* Comptes Rendus, 1877, p. 910. 
