46 DISEASES OF DECIDUOUS FOREST TREES. 



a very smooth, rounded edge, which in most cases is light brown, 

 appearing as if polished, or sometimes somewhat villous. The older 

 parts of the upper surface are dark brown, almost black, and are 

 broken into many small pieces by numerous fissures. Many old 

 sporophores have a jagged, extremely rough surface because of these 

 fractures. Lichens and moss frequently cover the older parts. 

 The lower side of the sporophore is dull red-brown and the interior 

 is light brown, with evident, though imperfect, indications of strati- 

 fication. The pores are continuous through several layers, remaining 

 open for two or three years. 



The sporophores often develop from the openings of tunnels of 

 the locust borer or from broken branch stubs. It is not unusual to 

 find eight or ten sporophores on one diseased tree. 



Wood which is decayed by Fomes rimosus when cut from the tree 

 will remain unchanged for a great many years. In other words, the 

 fungus will not continue to form fruiting bodies on such decayed 

 wood as does the false-tinder fungus previously mentioned. The 

 only preventive measures which can be taken are to care for wounds, 

 and preferably to cut all locust trees before they reach an age where 

 their branches begin to break off in large numbers. For most 

 localities this will be from sixty to seventy-five years. 



WHITE HEART-ROT OF ASH CAUSED BY FOMES FRAXINOPHILUS. 



A disease caused by Fomes fraxinophilus Peck upon white ash 

 (Fraxinus americana L.) in the Mississippi Valley has been described 

 in a previous publication by von Schrenk (84). It attacks white 

 ash trees of all ages, usually those, however, which are more than 7 

 inches in diameter. The fungus is a distinct wound parasite, the 

 parasite starting its development in a branch stub, whence it grows 

 into the heartwood of the trunk. The diseased wood first of all 

 turns darker in color. The next stage of the disease is marked by a 

 bleaching of the color in the spring wood of the annual rings; these 

 gradually turn back to the original straw color, and then white in 

 spots. Ultimately the whole tissue becomes a loose, spongy mass 

 of wood fibers. The completely rotted wood is straw colored, very 

 soft and nonresistant, and readily absorbs water. 



The sporophores of Fomes fraxinophilus appear at the base of 

 branch stubs or in wounds, either alone or several together. The 

 mature sporophore is nearly triangular in cross section; it has a 

 broad, rounded edge, which at first is white and gradually turns 

 darker until it becomes somewhat straw colored. The older por- 

 tions of the upper surface are dark brown or black and are very hard 

 and woody. The younger part grows out over the older portions, 

 which makes the sporophore look somewhat sulcate. The main 



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