DISEASES CAUSED HY WOUND FUNGI. 49 



willow (Salix sp.), ash (Fraxinus excelsior L.), birch (Betula sp.), 

 horse chestnut (Aesculus hippocastanum L.), and beech (Fagus syl- 

 vatica L.). Buller's descriptions refer especially to the occurrence 

 of this disease in Europe; and although the writers have found the 

 same but rarely in this country, it occurs now and then in the North- 

 ern States. Freeman (23) mentions its occurrence in Minnesota, 

 although ho states that it is usually found on dead logs or stumps. 

 In view of its widespread occurrence in Europe on living trees, it is 

 probable that it will be found in this country more frequently than 

 is known at the present time. 



According to Buller, diseased maple wood becomes much whiter 

 than the normal wood. Irregularly scattered series of white lines 

 appear in the diseased wood, resembling the decay brought about by 

 Fo/ttc* <ij>]>l<in<ifnx as described by Heald (38). 



The fruiting bodies are almost circular and are attached to the 

 trunk of the tree by a marked stipe. They grow to a considerable 

 size, individuals 1 foot in diameter not being at all infrequent, and 

 Buller mentions a sporophore which measured 2 feet 2 inches across. 

 He states that they are remarkable for their rapid rate of growth. 



The fruiting bodies are annual and are produced from May until 

 September. They are at first soft and juicy, but as they grow older 

 and drier they become very tough. The upper surface is character- 

 ized by the presence of a series of large scales, which give it a rough- 

 ened appearance. Buller states that when a tree has been killed by 

 Polyporus squamosus the fungus can still continue its annual produc- 



tion of fruiting bodies. 



TWO SAP-ROTS. 



In addition to the fungi which have been previously described, there 

 are two forms which are usually considered parasitic on deciduous 

 forest trees. These are Fomes fomentarius (L.) Fr. and Polyporus 

 betulinus (Bull.) Fr. Both of these fungi are very common all over 

 the Northern Hemisphere, and both of them have been described by 

 various authors (Tubeuf (102), Mayr (53), Hartig (34, 35), Freeman 

 (23), et al.) as parasitic on living trees. The manner in which they 

 attack trees, however, is so different from that described for the fungi 

 which cause distinct heart-rots of living trees that they should be 

 considered in a separate group. 



In spite of numerous observations which the writers have made 

 for years upon these two fungi, they are not prepared to class them 

 with the preceding forms, nor can they state definitely that they 

 should be considered as parasitic on living trees. Distinction between 

 a parasitic fungus growing on a forest tree and one growing as a sapro- 

 phyte is a difficult matter. The writers have attempted to make two 



149 



