MISTLETOE INJURY TO CONIFERS. 1S 
most cases brooms are initiated on the Douglas fir soon after infec- 
tion. Young seedlings frequently die in the top, owing to the forma- 
tion of a lateral broom midway on the stem. In the heavily infected 
regions of Montana, especially in the Clark Fork (Bitterroot and Mis- 
soula Rivers) drainage, brooming of the Douglas fir is so universal 
and of such extent that scarcely a single infected tree is free from 
brooms of some type (figs. 6 and 7). The structure of these brooms 
is very plainly shown if the tree succumbs to the parasite, as it often 
does (fig. 7). The formation of brooms invariably results from mis- 
tletoe infection on 
the western larch. 
They may be situ- 
ated on any part of 
the branch or at its 
base (fig. 14). In 
the latter case the 
entire branch even- 
tually dies or is 
broken off by the 
wind, and its place is 
usually taken by a 
series of short, 
scrubby secondary 
branches forming a 
trunk broom. This 
broom _ eventually 
dies, leaving a large 
knotty burl of seri- Fic. 12.—Typical broom on yellow pine caused by Ruzou- 
ous consequence not mofskya campylopoda. Note that the end of the branch 
only to the life of the a 
tree but greatly decreasing its value for lumber. Excessive brooming 
is a common feature wherever infected larch occurs and is the chief 
cause of injury to the species. In some localities in the Blue Moun- 
tains of Oregon and parts of Idaho and Montana, where this mistletoe 
is common, a normally formed larch is seldom found. Instead of the 
symmetrical, conical crown so characteristic of the normal tree, the 
crown develops under the influence of the parasite into a denuded 
spike, bearing only a few ragged branches. When it is recalled that 
practically every larch in these regions, from pole size up, is more or 
less infected and seldom attains a normal size, in many cases being 
killed outright, some notion may be had of the seriousness of the 
effects of the parasite on its host. 
