234 STATE POMOLOGICAL SOCIETY. 



assumed so decided a prominence, relatively speaking, as it has done since, 

 upon our virgin soils, it has blossomed forth into the noble and luscious varie- 

 ties which American pomology has given to the world. 



Although this fruit comes to us as an importation from the old world, its 

 already lengthened trial, under all the varying circumstances of our fitful 

 climate, with the additional difficulties of widely varied soil and aspect, has 

 long since demonstrated that, with the possible exception of the apple, no one 

 of the many European pomological contributions to our country, has been 

 found more perfectly adapted to the exigencies of the case, so far as the mere 

 question of hardiness is concerned. In fact, the tree is seldom, if ever, found 

 to suffer from the severities of our climate, unless previously weakened by 

 disease or the over-production of fruit ; while, unlike the peach, its fruit buds 

 are rarely winter-killed, from undue autumn development or other cause. 



BLACK KKOT. 



The plum tree, in our country, is liable to but few diseases; and but one of 

 these, the Black Knot, has, so far, proved to be of a serious character. The 

 investigation of this disease, from the very nature of the case, is beset with 

 difficulties, and, as a consequence, theories have been, and still are, numerous. 



Among the many observers of this malady, during its earlier history, were 

 several gentlemen of "Western New York, who became persuaded that they had 

 discovered its cause in the operations of an insect which punctured the shoots 

 and deposited its eggs in the wound. These observers claimed also to have 

 discovered that, with its eggs, the insect in question, at the same time, 

 deposited a poisonous substance which, acting upon the flowing sap, at and 

 near the punctured spot, produced the diseased growth in question, the same 

 becoming developed upon the surface on or about the third year after the 

 occurrence of the puncture. The remedy devised to meet the demands of this 

 theory was the careful removal of the punctures by excision and the applica- 

 tion of a disinfecting wash to the wounds, for the purpose of neutralizing any 

 possible remains of the infection. Specimens of the insect and also of the 

 punctured shoots were sent to B. P. Johnson, of Albany, New York, and were 

 by him submitted to Professor T. W. Harris, of Massachusetts; who, without 

 expressing an opinion upon the cause of the malady, or the agency of the 

 insect in producing it, identified the alleged culprit as a " leaf hopper," known 

 in scientific parlance as *' Memhracis Bubalus." 



Other observers seem to have reached the conclusion that the curculio, at 

 the season for depositing its eggs, failing to find a supply of fruits, resorts to 

 the young shoots for that purpose, and in so doing, so far poisons the circula- 

 tion as to occasion the unsightly and injurious excrescences complained of. 



Another class of observers have advanced the idea (of course without a pos- 

 sibility of demonstration), that this abnormal growth is a mere " vegetable 

 nicer;" but they do not even attempt to assign it to a specific cause. 



William H. Eead of Port Dalhousie, C. W., in The Horticulturist for May, 

 1855, claims to have given the subject many years of close and careful observa- 

 tion, and advances the theory that the disease is the result of the decay of the 

 fruit, in contact with the branch, during the warm weather of August and 

 September. 



Each of these theories, when propounded, seems to have secured more or less 

 advocates, but no one of them has succeeded in more than partially and, we 

 may add, temporarily establishing itself in the confidence of those whose opin- 

 ions on tlie subject may be entitled to respect. 



