MISTLETOE INJURY TO CONIFERS. 25 



outer central area of the burl die soon after the death of the cor- 

 tex, especially in burls on the larch, and open wounds are formed, 

 inviting the attack of forest-tree insects and wood-destroying fungi 

 (fig. 24). The abnormal thickness and the soft, spongy consistency 

 of the inner bark of mistletoe-infected branches are attractive to 

 various gnawing animals; they are also an index of the storage of 

 food materials at this point (fig. 25). 



PIG. 24. Cross section of a burl on a western larch caused by Razoumofskya laricls. 

 Diameter of burl, 2 feet. Note the presence of borers and fungi. The check ap- 

 peared in seasoning. 



RELATION OF MISTLETOE INJURY TO FUNGOUS ATTACK. 



Some very interesting data have recently been assembled by the 

 writer on the relation of mistletoe burls to fungous attack. From 

 cutting areas on the dry bench lands of northern Idaho, 540 mistle- 

 toe-infected living larches were examined. Out of 600 mistletoe 

 burls found on these trees, 278 were inhabited by serious wood- 

 destroying fungi and other unimportant species. According to 

 frequency of occurrence the most important of these fungi are 

 Trametes pini (Brot.) Fr., Fomes laricis (Jacq.) Murr., Polyporus 

 sulphureus Fr. (four occurrences at 20 feet up on the trunk, a very 



