Even to this day there are excellent horticulturists who doubt whether small microscopic organisms in the vegetable kingdom are capable of originating disease in plants. They believe they always follow disease. To these, such a report as this will be welcome if they have any desire to learn how far they may be wrong. Mr. Arthur shows that, when persons talk of fungi they refer to as many forms of vegetable beings as they would if discoursing of the higher grades of flowering plants. There are thousands of them, and just as there are parasites among higher plants and plants that feed parasites, - so there are funguses that will injure other plants, and funguses that are no harm at all. The gray color, familiar to all who know lilac bushes, and called lilac-mildew, comes from a small fungus known as Microsphaeria Friesii, - it does not injure a lilac bush; but the potato fungus, Perenospora infestans, undoubtedly kills its host. So with remedies. Though sulphur is a foe to many kinds of these lower forms it is quite likely some one would find a fungus that would grow and wax fat on a block of sulphnr.

In this paper, Prof. Arthur studies the fungous diseases of the apple, pear, quince, peach, tomato, oats, clematis, and Canada thistle. He goes over again the work of Prof. Burrill, in regard to Bacteria causing Fire-blight in the pear, with results confirming them. The great difficulty we find in following Prof. Arthur in his details is the uncertainty whether we all understand the same thing by the same terms. He considers Twig-blight and Fire-blight as synonymous, yet, what most fruit culturists know as twig-blight is certainly the work of an insect, and the two terms would not be generally regarded as synonyms. This confusion then naturally results in the question, do these gentlemen mean the same thing by Fire-blight as we do ? Prof. Arthur's idea is that the chief characteristic is the blackening of the branches and foliage, usually accompanied with a peculiar putrefactive odor. But there are several troubles that are characterized in this way that are certainly not due to the causes that produce what most fruit growers know as Fire-blight. There is a sudden blackening of the leaves that seldom reaches even the petioles, very common among pear-trees about midsummer; and there is a blackening of the leaves and young stems soon after they push in spring, and which the old folks, for want of better knowledge, called " Frozen-sap blight," which, no doubt, of fungus origin, is not Fire-blight. And then we know that the true Fire-blight starts at some fixed spot on a branch, killing the tissue only for a few inches, and that it is only when the branch is literally girdled for these few inches, thus stopping the upward flow of the sap, that the upper leaves turn black, presumably for want of food.

Yet, as we understand it, bacteria are found in these black leaves, as they are in all decaying substances, and we have not been able in our minds to connect the bacterium introduced into a four or five year old branch by inoculation, and which may girdle it, with the bacterium found in the dying leaves, because there is so much bark tissue uninjured between the dying leaves and the small spot where the enemy's attack was made.

Again, Prof. Arthur regards the " Apple-blight" and Pear (Fire) blight as identical in origin. But there are so many forms of "blight" in the apple, that must have different originations, that we again wonder whether the author and reader can possibly mean the same thing. There is one kind that seems to start early in the spring by eating away both wood and bark, getting deeper and wider each year, but only once in a while extending wholly round the stem. It may work for several years before it gets completely round, but when it does the whole foliage above blackens and dies - not quite - but nearly as suddenly as in the usually recognized "Fire-blight." Another form seems to delight in operating at the point of junction with a branchlet and branch. In this case a tree often presents the peculiarity of nearly all the smaller branchlets in the interior of the tree with browned or blackened leaves. When the leading branches die we have rarely seen more than the growth of the last year suffer; we do not know that we ever saw an aged branch, or a whole tree, go off "in a night" as we find in the pear-tree they often do.

These different experiences lead one to doubt whether the author and the reader have the same ideas when the same terms are used; and we believe it is because this uncertainty very frequently arises that the conviction which the authors of such treatises as this hope to carry to the reader's mind, fail to have the desired effect.