MISTLETOE INJURY TO CONIFERS. 1833 
With the conclusion of this general statement of mistletoe injury 
a more detailed discussion of the various types of infection will 
now be taken up. 
RESULT OF INFECTION ON THE BRANCHES. 
One of the first effects of infection, either of stem or branch, is 
the formation of a fusiform swelling (fig. 10). Sometimes this 
swelling is very pronounced and may resemble the enlargements 
caused by some species 
of Peridermium (fig. 
11). The swelling is 
the first stage of the 
future hypertrophy 
commonly known as 
witches’-brooms. The 
absence of any pro- 
nounced brooming 
from early infections 
has led some observers 
to the conclusion that 
brooms are never pro- 
duced on some conifers. 
Any change from the 
normal branching is 
here considered a 
broom. Still it is not 
necessary to draw such 
sharp. lines, as the 
brooms produced by all 
mistletoes of the gents 
in question are quite 
typical. It May fYre- Fie. 9.—Western hemlock (Tsuga heterophylla) infected 
quire several years for by Razoumofskya tsugensis. These trees do not possess 
a a single normal branch. All are broomed. The trees in 
the broom to form. If the background are spike topped. The tree in the fore- 
young trees are gen- ground has had its growth in height arrested by an 
immense terminal broom. 
erally infected they 
sometimes assume an open, ragged appearance, which to the casual 
observer would not be considered a broom (PI. III, fig. 2). Never- 
theless, the tree is no longer excurrent. <A similar condition is 
sometimes noted in more mature larches, where the infection is so 
generally distributed throughout the entire crown that no typical 
brooms are produced for years. Heavily infected branches of old 
trees of all species are seldom without brooming of some kind, and 
in most cases typical brooms are formed. The mistletoe plant may 
die out entirely on very old brooms, especially those of yellow pine 
