294 STATE HORTICULTURAL SOCIETY. 



in any casual relation to yellows, but all are likely to be found wherever the 

 peach is grown in the United States. Those which show any special prefer- 

 ence for diseased trees — c. g., Ccrcospora (?) — are not confined to trees suf- 

 ferinfy from yellows, but occur equally on all trees of low vitality, and are 

 clearly a consequence of impaired vitality rather than a cause. 



On the parts underground I have found no species of Agaricu^, and have 

 almost never observed any growing in orchards. 



Altogether, I have more or less fully examined the root system of fifty-two 

 good sized trees, all of which were unquestionably diseased by yellows. In 

 every instance the main roots, and all their ramifications down to those smaller 

 than a goose quill, were perfectly sound. The bark was bright colored and 

 sound throughout, and the wood was free from black spots, rottenness, or 

 signs of decay. Certainly it was not disorganized by mycelial threads of any 

 sort, nor were these commonly present on the surface of the smooth bark. 

 My own observations agree in this respect with the greater part of those here- 

 tofore reported. All the larger roots are healthy. 



I have, however, sometimes observed a delicate cobweb fungus on the- 

 smaller roots and on the rootlets of diseased trees, and have in almost every 

 instance found a large portion of these rootlets dry and dead, even where no 

 fungus could be detected by the naked eye or by the use of a triplet. If 

 peach yellows is in any sense a root disease, I predict it will be found con- 

 nected in some way with the destruction of the feeding fibers or root hairs of 

 the tree. Ilowevt r, the dead rootlets may be a consequence of the disease 

 rather than a cause, and such a view seems more in harmony with the results 

 of some of the inoculations. I do not feel like pronouncing very decid- 

 edly on the matter until the inoculated trees have stood another year, 

 and until I have made the most prolonged and painstaking underground 

 explorations, accompanied by careful microscopic examinations. An additional 

 season in the field and a year of laboratory work would throw much light on 

 the question. Concerning 1 he supposed relation of bacteria to this disease, 

 not enough microscopic examinations or culture experiments have been made 

 to venture any conclusion. On or in the diseased tissues I have occasionally 

 observed a bacillus much resembling that found by Prof. T. J. Burrill and 

 Dr. Manly Miles; but he would be a very rash man who, on the strength of 

 the occasional and perhaps entirely accidental presence of these all abound- 

 ing micro-organisms, should assert their casual connection with this disease. 

 Opinions of any value cannot be given until after an exhaustive study of the 

 diseased tissues. No one has yet undertaken this, and no one is now com- 

 petent to speak with authority. 



The rapid spread of the disease in certain years, together with various 

 other facts in its history, lead me to believe that it is due to a parasite of some 

 sort. I have observed much that is very suggestive, and nothing that is in- 

 consistent with such a belief. Even the fact that the disease has existed in 

 some localities for many years without becoming widely destructive is not 

 opposed to this view, but could be paralleled by many references to animal 

 and plant diseases now well known to be of parasitic origin. Certain external 

 or internal conditions of the host plant, or animal, or peculiarities of locality, 

 not yet well wnderstood, are almost always necessary to the rapid dissemina- 

 tion of a parasitic disease. If these are wanting, the disease will be confined 

 to limited areas or to isolated cases. 



If yellows is due to some root fungus or other underground parasite, it 



