16 



the season the black surface of the knot shows to the naked eye, on 

 close examination, a division into many minute facets or regions, 

 separated by slight furrows. Microscopic study shows that each of 

 these facets corresponds to a cavity which finally communicates with 

 the exterior by a pore at the middle of its facet. In these cavities 

 are developed the tointer spores^ which become ripe and are set free 

 in late winter and early spring, and, presumably, produce the begin- 

 nings of new knots at that time. 



Nearly all our knowledge of this fungus is due to the admirable 

 account of it in Part V. of the Bulletin of the Bussey Institution, by 

 Prof. W. G. Farlow, of Harvard University; but further study is 

 needed of the manner in which the infection of the branches of the 

 host by the spores of the fungus is accomplished, and of the early 

 history of the development of the knots. When a tree has become 

 badly infested with the knots not much can be done except to prevent 

 its continuance as a spreader of contagion, by cutting it down and 

 hurtling it. Simple cutting down is not sufficient, for Dr. Farlow has 

 shown that knots on a tree, cut down in summer and allowed to lie 

 through the winter, developed their winter spores as if the tree had 

 been standing. 



The treatment which has been recommended is that the knots be 

 cut off and burned, as fast as they appear. This often leads, how- 

 ever, to very serious disfigurement of the tree, and a less heroic 

 remedy is much to be desired. A treatment similar to that recom- 

 mended in Bulletin No. 4, of this Station, namely, the painting of 

 the knots with a mixture of red oxide of iron in linseed oil, has given 

 very good results in case of young trees on the private grounds of 

 Dr. C. A. Goessniann, Director of the State Experiment Station. 

 This preparation seems to stop the development of the fungus so that 

 the knots crumble and fall away, with the least possible injury to the 

 branch. Even were its effects not so complete, such an application 

 would be useful in preventing the dissemination of the spores of the 

 knot-fungus. In connection with this painting of the knots, special 

 fertilizers have been applied to the soil about the trees, with the 

 object of lessening their susceptibility to the attacks of the fungus. 



A very serious difficulty in dealing with a disease of this sort is 

 presented by the fact that one man who is intelligently and persist- 

 ently fighting it by destroying all his old trees and carefully treating 

 the young ones, may be surrounded by and constantly exposed to old 

 trees belonging to neighbors, who have too little energy or public 



