not show near as much of the fungoid growth as did the larger, and, indeed, I examined several sections before I found any mycelia at all. In both cases it was situated on the under side of the inner bark, next to the cambium layer, and many of the filaments penetrated and ramified through this layer. I also noticed, in the larger specimens, mycelia between the layers of wood. An examination of the abnormal pigment spots, scattered through the pith and woody portions, revealed nothing but cells filled with the coloring matter. The outer bark in no case showed signs of any fungoid forms.

3. Branches. An examination of the larger branches revealed nothing at all different from that given above for the trunk of the tree; but some of the smaller branches and the growing ends of the larger or main branches, showed marked peculiarities indeed. In these the tissues seemed to be completely filled with mycelia, and in one case the bark was apparently split.1 The branches from which these specimens were taken had many abnormal branchlets, and hence the theory advanced in the first part of this paper that these abnormal shoots were caused by the filling up of the tissues of the growing ends, thus turning the flow of sap to the lateral buds.

The filament found in the branches was in all respects identical with that found in the trunk of the trees, and will be described further on.

4. Leaves.-Those examined were mostly from the abnormal branchlets. The chlorophyl in all was completely disorganized, and in general the appearance was the same referred to by Mr. Peck. It seemed at first that this must be caused by dry weather or lack of cultivation, but on further examination filaments of a fungus were found to be present, to a greater or less extent, in nearly all the leaves examined. I noticed but two spores of any sort in the tissues, these were teleuto-spores and without doubt belonged to some leaf fungus other than the one the filaments of which were found in the tissues. On a few of the leaves sent me I found the fungus Ascomyces deformans, which causes the "curl leaf" disease so common at the present time in many localities.

The filaments of the fungus alluded to first, were of the same character as those that will be described under the next head,

A friend to whom I showed this, suggested that this splitting might have been caused by the pressure of the growing mycelia within the tissues.

Mr. Thos. Taylor says, that ""it is evident that the healthy leaves possess an antiseptic substance which prevents the growth of the common moulds on them." The results of my experiments have led me to the same conclusion. An analysis of the

FIG. 5—A, fruit of a fungus found just beneath the skin of the peach. This resembles a portion of the fruit of the Saprolegnieæ (× 406); B, spores formed in the peach. Drawn with the camera lucida (× 406).

leaves show that there is a much larger proportion of moisture in the diseased leaves than in the healthy. I analyzed several specimens of each and found a greater difference between them than Mr. Taylor reports. However, this is not important, as the per cent. may and does vary much. The average of my analyses was as follows:

There is a small per cent, of volatile matter in the leaves that in the estimation would raise the per cent. of moisture slightly. It will be seen from the above results that the unhealthy leaves are much better fitted to become the host of a parasitic fungus than are the healthy ones.

As to what causes this abnormal amount of moisture, I have already formed an opinion, but desire to confirm it by further experiment, the results of which I hope to include in a future paper devoted entirely to this subject.

5. Fruit. I found that the most satisfactory results were to be obtained from an examination of the fruit, and therefore spent the greater part of my time upon that portion of the tree. Mycelia in abundance were found just beneath the skin, extending into the fleshy parenchyma a short distance. This fungus-identical with that found in the other parts of the tree—was unicellular, branching, and much enlarged in places. In some places the filaments were apparently filled with small oil globules and bodies closely resembling spores. In only a single instance did I find a distinct fruiting filament. That I did not find more of the fruit I regret very much, for in order to know fully the characters of a fungus, its fruiting system must be carefully studied.

The single specimen of the fruit I examined is shown on Fig. 5. It was found beneath the skin of a prematurely ripened peach, detached from the remaining filaments present with it, and yet evidently it belonged to the same growth.

Several peaches were examined, and in no case did I fail to find the same branching form.

The method of branching and the form of the filament (shown on Figs. 3 and 4), as well as the oil globules which they contained, and the fruiting system of this fungoid growth, immediately reminds one of Saprolegnica, to which division of fungi this form seems to belong. And as the final result of my investigation up to the present time, I believe this parasitical vegetable form to be at least a part of, and probably the whole cause of this disease.

Many modes of procedure have been suggested to effect a cure

and thus save the trees. Those persons advancing some of them claim that their modus operandi is a sure and active agent in bringing about the desired end. But most of the modes are simply theoretical and always fail. In most cases when a cure has been reported, it has afterwards been proven that the tree did not have the yellows at all. For example, one who attributed the yellows to an animal origin, used Paris green, throwing it over the tree with a pump, and the next year the trees that he supposed to be diseased were in a healthy bearing condition. It was afterwards shown that the symptoms of the yellows were

X406

FIG. 6. Hairs on the skin of the peach (X 406). Drawn with camera lucida. produced indeed by an animal, but that animal was simply a plant louse! The tree being covered with them, the Paris green was an effective agent in ridding the orchard of its pest.

Some have used hot or boiling water, pouring it about the roots of the trees, and in many cases they have reported the disease reduced; but in every case that has come under my observation it has failed.

It is not at all surprising that the means used—including the whole category of remedies-have often been reported as producing a satisfactory cure, for many of the temporary injuries liable to come upon a tree, will, in most instances, produce many of the symptoms of the yellows; these are the cases that have been

cured. If they had been left alone nature's physician would have cured them also. Nature does not cure the yellows. A severe frost will kill the heart wood of a tree, producing some of the characters of this disease, but the exterior-the vital partremaining unharmed, it will soon return to its healthy condition.

Disinfectants have been recommended. Mr. A. G. Gulley says upon this subject: "But I look with hope in another direction, that of preventives by which we can disinfect the trees or enable them to resist or throw off the disease. This idea is strengthened by the evidence that a fungus may be the cause. We know that the low forms of vegetable life are destroyed by various substances and cannot exist in their presence. If the disease is of that nature, by the introduction of some of those materials we shall disinfect the trees, destroy the germs or prevent its growth."

We agree with Mr. Gulley in this, but as far as experiments have been tried, the right substance has, as yet, not been found, and it is a query whether or not the very agent that may be destructive to the fungus may not also, being unnatural in the circulation of the tree, destroy it also.

Mr. Taylor2 recommends the use of sulphates and alkalies as a wash to be used on the bark and roots of the trees. It must be borne in mind, however, that he is inclined to attribute the disease to the agency of a species of Noemaspora, which I think has been clearly shown is not the cause, but that the fungus that produces the yellows, both fruit and mycelia, is more internal than he claims, and would thus necessitate the introduction of the acid, alkali or any disinfectant into the circulation, which would produce an abnormal condition of things physiologically, and injure the tree itself. I have no doubt, however, that if enough of these reagents were used the fungus would be destroyed.

Dr. Kedzie's recommendation1 of the use of potash and phosphoric acid or superphosphate of lime as an experiment, we consider as simply a good preventive, and have discussed it under that head.

From my work and observations, and from, I think, a scientific standpoint, letting theories alone, the only cure that I can recommend, is, that the fruit grower, when he notices that any tree in his orchard has become diseased, root it out carefully and burn 1 Mich. Pomological Report, 1878, p. 252.

2 Mich. Pomological Report, 1872, p. 596.