eit 
99, BULLETIN 360, U. S. DEPARTMENT OF AGRICULTURE. 
ous, large barrel-shaped swellings, from which pitch usually exudes 
in large quantities. Infection on one side of the tree generally re- 
sults in the type of burl shown in 
figure 19. 
Burl formations resulting from 
mistletoe are a common feature 
bE AAT TT EP 
Fic. 19.—Common type of purl on yellow 
pine caused by Razoumofskya campyle- 
poda. The tree is 3 feet in diameter at 
this point. 
on western hemlock wherever the 
parasite occurs in quantity. The> 
same is true for the mountain 
hemlock. In the Marble Creek 
region of the St. Joe National 
Forest mistletoe burls on the 
hemlock are of frequent occur- 
rence. Allen (1, p. 20-21) writes 
of this type of injury as follows: 
“Tf, however, the plant gets 
foothold on the leading shoot, a 
burl follows which persists 
throughout the life of the tree 
and not only ruins a log, but ren- 
ders the tree apt to be broken by 
the wind.” Infection on the main 
trunk of lodgepole pine is often 
attended by long fusiform swell- 
Fig. 20.—-Main stem of a lodgepole pine in- 
fected by Razoumofskya americana. Note 
ings as the parasite progresses 
from the original point of in- 
fection. This may continue until 
the spread of the parasite from the original 
point of infection. The bark at this point 
very frequently dies, leaving an open wound. 
(Photographed by George G. Hedgecock. ) 
_ the bark becomes so hard that the plants can not push up through 
it and the spread of the parasite ceases (fig. 20). The parts 
