1893.] PUBLIC DOCUMENT — No. 33. 237 



matured two crops of spores and done its work, and to 

 remove it is a waste of time and labor. But just beneath it 

 on the l)ranch, and on each of the side branches, is a smaller 

 iind less conspicuous swelling, whose bark is just bursting. 

 These swellings are knots a year younger than the large one, 

 and have ripened no spores. The thorough removal of these 

 is preventive work of the best kind. I lirmly l)elieve that a 

 man who will start with healthy trees and will carefully 

 examine them for these young knots about the last of April 

 in every year (for the climate of Massachusetts), thoroughly 

 removing and burning all that are found, need have very 

 little fear of black knot. AYliere a small branch is attacked, 

 one need only cut it off some distance below the knot. 

 Where, as wall rarely happen if trees are carefully looked 

 after annually, a large branch whose removal would seriously 

 injure the tree is involved, the knot may be carefully dug 

 out until healtliy bark is reached in all directions. The 

 •exposed tissues may then be painted over with a heavy coat 

 of red oxide of iron in linseed oil. This coating will serve 

 as a protection, and will also, by its color, enable one to 

 readily find the treated spots and to watch them for any 

 further development of the fungus. The application of 

 kerosene to the knots, while doubtless fatal to the fungus, 

 is likely to be equally so to the tissues of the tree, and is 

 not to be recommended as a general practice. 



For the greatest success in dealing with the black knot, it 

 is, of course, a prime necessity that sources of infection 

 shall l)e reduced to a mininumi. Neighboring plum or 

 cherry trees or wild plants of the various native species of 

 l^lums and cherries may serve as propagators of the fungus, 

 and make one's labors much greater and his chances of 

 success much smaller. The great desideratum in this 

 regard is an intelligent and active public sentiment, which 

 shall compel the destruction of all such plague-breeders. 

 A few of our States have accepted the suggestion that 

 the matter be made the subject of legislation, and have 

 enacted laws to compel the destruction of trees infected by 

 the black knot. One may, however, well doubt the utility 

 of such legislation. It is interesting, as showing the begin- 

 ning of toleration for subjects which, not long ago, would 



