MISTLETOE INJURY TO CONIFERS. 



21 



the increasing age of the host the burl tissues radiate outward in a 

 fan-shaped area when viewed in cross section and soon leave an open 

 wound, through the death of the central part of the infected wood. 

 These two types of burl are so common on larch in mistletoe regions 

 that the quality of the wood is seriously injured, resulting in a 

 large amount of cull. In the several regions studied by the writer 

 mistletoe burls on yellow pine are frequent. In one section of the 

 city park at Coeur d'Alene, Idaho, are 30 or 40 large, old yellow 

 pines. About half of the trees have mistletoe burls on the first 



FIG. 18. Cross section of a mistletoe burl on the yellow pine shown in figure 17. 

 (The tape shows feet in tenths.) 



log length and in most cases the parasite is still living in them, 

 with a few scattering short aerial parts. Similar conditions pre- 

 vail throughout the Spokane River Valley and around Coeur d'Alene 

 Lake. Mistletoe burls on old yellow pine may or may not be con- 

 spicuous. Frequently there is no pronounced swelling (fig. 17) and 

 sometimes the only means of detecting the diseased condition is by 

 the presence of the mistletoe or an unusual roughness of the bark. 

 A section through the tree at this point, however, shows the curly 

 grain and the old roots of the parasite extending to the point of 

 original infection (fig. 18). These burls are often very conspicu- 



