26 



BULLETIN 360, U. S. DEPARTMENT OF AGRICULTURE. 



unusual habitat), Trametes serialis Fr., and Lenzites sepiaria Fr. 

 Fomes pinicola Fr. was found rotting the heartwood of living trees 

 in three different cases and had entered its host through mistletoe 

 burls 10 feet from the ground. Polyporus volvatus Pk. occurs fre- 

 quently on the burls of larch and yellow pine. Several species of 

 Thelephoraceae were collected from the mistletoe burls, chief of which 



were Stereum sulcatum Burt, 

 Corticium "berkeleyi Cooke, 

 C. galactinum (Fr.) Burt, 

 and Peniophora s u l> s u I - 

 phurea (Karst) Burt. Cera- 

 tostomella pilifera (Fr.) 

 Wint., the bluing fungus, 

 appeared occasionally in the 

 dead wood of the burls. 

 Trametes pini affected 80 

 per cent of all burls attacked 

 by fungi. Since the most 

 advanced stages of decay 

 were always at the burl or in 

 its near vicinity, it was as- 

 sumed that the fungi had en- 

 tered at this point. The de- 

 cay at or in the burl tissues 

 was in most cases not con- 

 nected with the decay which 

 is often present in other 

 parts of the trunk. The 

 breakage of old branches 

 possessing heartwood, 

 through the accumulation of 

 brooms at their outer ex- 

 tremities, is likewise a means 

 of fungi entering the tree. 

 Not infrequently F o in e s 

 laricis enters its host by this 

 means. Mistletoe burls on Douglas fir are known to become infected 

 with Trametes pini. A mistletoe burl on Alpine fir was found to be 

 inhabited in one instance by Pholiota adiposa Fr. Meinecke (10, p. 

 58) refers to the mistletoe cankers of Abies concolor as offering an 

 easy entrance to germinating spores of EcMnodontium tinctorium. 

 Burls on yellow pine, owing to their resinous condition, are seldom 

 attacked by wood-destroying fungi. The bluing fungus, however, 

 has been found by the writer in the distorted tissues of mistletoe 

 burls on living yellow pine. 



FIG. 25. The soft spongy cortex of a mistletoe 

 infection on lodgepole pine gnawed by rodents. 

 This is a very common type of injury in mistle- 

 toe-infected trees. 



