16 



BULLETIN 360, U. S. DEPARTMENT OF AGRICULTURE. 



The brooming of the branches of the lodgepole pine by mistletoe is 

 as characteristic as for the other hosts mentioned. Frequently the 



entire tree is involved, 

 but more often only 

 the lower branches. A 

 f ew instances have 

 been noted where the 

 parasite hung in long 

 festoons from the sev- 

 eral infected branches 



FIG. 13. Typical broom of the weeping-willow type on Doug- 

 las fir caused by Razoumofskya douglasii. Note the long, 

 flowing branches. Sometimes these branches are 8 to 10 

 feet long. 



without any particular hypertrophy of the 

 branch as a whole. This condition is more apt 

 to occur in dense stands. Observations by the 

 writer on Picea engelmanni, P. mariana, 

 Abies grandis, A. lasiocarpa, A. concolor, A. 

 magnified, Tsuga heterophylla, T. merten- 

 siana, Pinus monticola, P. alUcaulis, P. flexi- 

 lis, P. attenuata, and other conifers show that 

 brooming of the branches is a common phe- 

 nomenon attending mistletoe infection of 

 these species. 



The weight of these brooms on many coni- 

 fers is frequently sufficient under stress of 

 winds and rain to cause the branches to split 

 from the trunk, or to break farther out if the brooms are located far 

 out from the trunk. This very commonly occurs in the case of 



FIG. 14. Typical brooms of old 

 infections on western larch 

 caused by Razoumofskya lari- 

 cis. Very few of the origi- 

 nal branches remain, and 

 they are heavily broomed and 

 covered with lichens. The 

 old branches are replaced by 

 short scrubby secondary 

 branches. Note that two of 

 the original branches still re- 

 main, but are dead. 



