Atmospherical Influences 67 
and a thinning of the top, or in under-development of the 
foliage, the latter being smaller, assuming a pendulous 
position and early fall coloring. 
The best preventive, where this kind of loss is anticipated, 
consists of pruning and mulching well, in order to restore 
the proper balance between 1oot and crown. 
Winter cold will, of course, affect the young and imma- 
ture twigs in the same way as do the late frosts. 
In smooth-barked trees, such as the Beech and Horse- 
chestnut, and in special situations, the bark of branches and 
young trees cracks in patches, and the cambium and the 
young wood underneath are killed. If such lesions are 
extensive they may lead to the death of branch or tree. 
This injury generally takes place on the southwest side and 
toward the end of winter when rapid temperature changes 
are more common; a few warm days stimulate the cambium 
on the south side to premature activity; freezing weather 
following, these active areas are killed, the young wood 
cells and cambium shrinking away from them and the bark 
cracking and drying out. Often not until summer does 
the bark split and reveal the damage below. 
Such frost phenomena as the killing of the bark appear 
in very variable form, such as small frost boils, or smaller or 
larger frost plates, the dead bark splitting off from the live 
margins and rolling back, exposing the dead wood, which 
then is either gradually covered up by a callus from the 
marginal cambium, or else becomes infested by fungi. 
The worst form of these frost injuries is the malformation 
known as canker, in which fungus parasites also take part. 
Wet, cool localities seem to predispose trees to this disease, 
but severe pruning and manuring in the spring may produce 
the same effect; this curiously enough, seems to appear 
as an individual peculiarity which can be transmitted by 
