40 Disease and Death of Trees — Generalities 
The “black” fungi, which attack the bark, find entrance 
through small wounds made by hailstones, insects, or break- 
ages. Working between bark and wood in the bast or 
bark portions of the cambium and into the wood, they 
destroy living tissue, and, if the injury is extensive in younger 
trees and twigs, they become dried out and killed. 
These bark-fungi are found especially on conifers, pine, 
spruce, fir, etc. Their presence is usually not discovered 
until a number of pin-sized, white, black, bright red, or 
yellowish pustules or spots — the fruit-bodies of the fungus 
—— appear on the outside of the dead bark. 
In deciduous-leaved trees the same class of fungi produce 
malformations known as canker. On small areas of irreg- 
ular shape the bark is killed, and in the attempt to heal the 
damage by callusing each season, and at the same time in 
the continuance from year to year of the fungus growth, all 
kinds of curious shapes of the wound are produced. Small 
fruit-bodies, white with minute red spots, appearing on the 
dead bark of the margin of the wound are the indications 
of the fungus causing these malformations. 
Similar to this disease is the black-knot of the plum and 
cherry trees, a fungus producing swellings of irregular 
shape. 
By reducing the water-supply, especially in dry years, 
these bark-infesting fungi cause sometimes the partial or 
entire death of twigs and branches. 
Various fungi working on young trees and on foliage give 
rise to swellings of the leaves like boils, and to the curious 
deformations known as “witch’s broom.” Timely removal 
of these arrests the progress of the disease. 
The condition and age of the tree determine, to a large 
extent, how far these fungus attacks may be detrimental. 
The vot fungi, which produce the decay of wood, are the 
