Periodical Literature 93 



The author found fungus filaments asso- 

 Root Fungi ciated externally with the rootlets of 



on basswood, beech, Paper birch, Shagbark 



Forest Trees hickory, hophombeam, ironwood, larch, 

 Black oak, Red oak, and White oak, while 

 the internal association of fungus with root-tips was found in case of 

 Black maple, Red maple. Silver maple. Black walnut, and horse 

 chestnut. No root fungi were found upon the Flowering dogwood, 

 American elm and Sassafras. Six forms of mycorhiza based on 

 color, arrangement of the filaments and the structure of the en- 

 closed rootlet are described. Four different kinds of mycorhiza 

 were foimd on one White oak tree, and they undoubtedly arose 

 from four different fimgi. The basswood roots have a fungus 

 that is both ectotrophic and endotrophic. Four species are added 

 to the list of fungi known to produce mycorhiza. This brings the 

 number up to nearly two dozen, and they nearly all belong to the 

 "toadstool" producing forms. 



The external mycorhizas appear to behave as annuals. They 

 begin to develop during the latter part of July; they are most 

 abtmdant in the fall and keep bright and healthy through the 

 winter, although the soil is frozen. By the middle of April they 

 begin to die off from the roots of some trees; from others by the 

 middle of May. Throughout June and the fore part of July 

 they are very scarce on all species. In August they begin to be 

 more plentiful again and by September they are as plentiful as in 

 September of the previous year. 



The author believes that the presence of the fimgus filaments 

 on the external surfaces of root-tips results in no mutual benefit 

 association, but is a case of parasitism on the part of the fungus. 

 An abundance of mycorhiza on tree seedlings may, indeed, prove 

 injurious to the extent of death. The conclusion that the fungi 

 are not beneficial is based on the fact that they occur most abund- 

 antly when the roots have the least need of them, namely, in late 

 summer and fall when the roots are relatively inactive and that 

 their occurrence at any time is purely accidental; trees get along 

 just as well without them. The conclusion that they do not help 

 in the absorption of nutrient salts is based on the fact that the 

 filaments disorganize the cortical cells of the rootlets and so make 

 absorption more difficult, if not impossible. That the fungi are 

 after food for themselves is indicated by the fact that they attack 



