greatest interest and has furnished every possible facility. He will probably enter upon systematic hatching of the mackerel next summer with a view to stocking other waters. It is hoped that at least Narragansett bay may be reached as a northerly limit. The artificial propagation is entirely feasible and the season being in mid-summer would not conflict with the shad season of the spring, the salmon season of the fall, or the cod season of the winter. The eggs are much more abundant, and hatch more easily, as well as more speedily, than any other fish now propagated. During the four days consumed in hatching a lot of shad, five lots of mackerel could be hatched, and during twenty-four days necessary to hatch one lot of codfish, thirty-two lots of mackerel could be produced. Mr. Earll selected a suitable locality for a hatching station at Cherrystone, Md., on the eastern shore, preferring this to Mobjack bay at which the pounds are most numerous, on account of an excellent harbor. The fishermen are also very kindly disposed, and offered to render every assistance. Thus most important facts are added to the natural history of the fish and the prospect is bright for a great commercial success. ANTHRAX OF FRUIT TREES; OR THE SO-CALLED FIRE BLIGHT OF PEAR, AND TWIG BLIGHT OF APPLE, TREES. By T. J. BURRILL, of Urbana, Ill.. THE widespread and disastrous disease of the pear tree, commonly called Fire Blight and that no less prevalent, at least in the western states, usually known as Twig Blight of the apple tree, are due to the same immediate agency. They are identical in origin and as similar in their pathological characteristics as are the trees themselves, or differ no more than one familiar with the histological structure of the trees might indicate, prior to observation upon the course and consequence of the malady. The quince and probably many other plants, among which we now name the butternut, the Lombardy poplar and the American aspen, suffer from the same disease. Judging from published descriptions only, it is also very probable that the "Yellows" of the peach will be found due to a similar cause. The immediate and exciting cause of the disease is a living organism, belonging to a group of minute beings called bacteria which produce butyric fermentation of the stored carbonaceous compounds in the cells of the affected plants, and especially in those of the bark outside of the liber or fibrous inner layer. This organism, if indeed specifically different, is closely allied to the "vibrion butyrique" of Pasteur1 and the Bacillus amylobacter of Van Tieghem,2 now known to be identical with the preceding. The proof of these assertions is the burden of this paper. HISTORICAL. This disease of pear and apple trees has been known in this country over one hundred years, in varying degrees of virulence and remarkably irregular occurrence, throughout the United States east of the great plains bordering the Rocky mountains, sometimes doing inconsiderable damage and again killing such disheartening numbers of trees that planters have not dared to risk the cultivation of these favorite fruits except upon a limited scale. The planting of pears has been practically abandoned throughout large areas of the country, solely on account of the ravages of the disease in question. Apple trees, though as often attacked in the western states and much injured, do not so severely suffer, seldom dying outright from this cause alone. The quince is scarcely less injured than the pear. No topic has been more fully discussed in the meetings of the horticulturists, and none has a fuller literature in the periodicals devoted to rural affairs. Theory after theory has been advanced as to the cause and the cure, only to be overturned by subsequent observation and experience. Because an insect was sometimes found destroying a twig or branch, and an account of its operations published, many persons supposed that insects were the depredators and the sole cause of the mischief. But no competent entomologist now attributes the devastating "fire blight" to the direct work of insects. Downing3 argued and he had many 1 Comptes Rendus, t. 52, p. 344, 1861. 2 Comptes Rendus, t. 88, p. 205, 1879 and t. 89, p. 5, 1879. 3 Fruits and Fruit Trees of America, 2d ed., p. 646. supporters that the difficulty originated in the freezing of the sap, and its subsequent corruption in the tissues. Others believed they had traced the origin of the disease to the absence of essential elements in the soil, while still others attributed it to organic debility of the trees. Finally, when all visible or tangible agents were given up, and all theories proved inadequately supported by facts, the idea of destruction by fungi was theoretically advanced. In 1863, Dr. Salisbury of Ohio published an illustrated account of his microscopical observations, concluding that "blight" was due to a fungus which he named Sphærotheca pyri. Later investigations have by no means sustained this opinion, yet by many this paper is considered the most important one in the literature of the subject. Dr. Hull5 of Illinois in 1868 and '70 gave accounts of observations and experiments, proving as he thought the accuracy of the fungoid theory. One of his statements is of special interest here. He had received through the mail a blighted apple twig and remarks: "We cut from it several small slices of bark, going deep enough to include a thin slice of wood; with these, we inoculated several succulent pear shoots by tying in the pieces of bark as in budding. After a lapse of thirty four days we found them all blighted." He also adds that the conditions of the weather were not the most favorable, for though warm, a drought was prevailing and he believed a humid condition of the atmosphere is required. Many others have stated, in a less definite way, that blight is communicable from diseased to healthy trees, but there is no precise account of carefully conducted experiments upon the subject. Professor Turner of Illinois speaks of its dissemination by the pruning knife, and cure by turpentine and lampblack. In 1868 Dr. Hull thought he had induced disease similar to the "fire blight" by grinding in water fibres of fungi found upon rotting roots. In an address before the American Pomological Society at St. Louis, Thomas Meehan gave his reasons for holding theoretically that the malady is due to fungous parasitism and, through the columns of the Gardener's Monthly, he has often pointed out the 4 Transactions Ohio Agricultural Society, 1863, p. 450. 5 Transactions Illinois State Horticultural Society, 1868, p. 35; 1870, p. 220. fallacy of other opinions and the accumulating evidence in favor of this. At his instance Dr. J. Gibbons Hunt, of Philadelphia, examined, by the aid of the best microscopical equipments, blighted limbs of pear, and having found a fungus which he supposed caused the black color of the branches, he says: "It attacks the bark and outside of the leaves and young fruit first, causing changes in the cells, in these locations resembling much those pigmentary cell-changes which differentiate the negro from the socalled white man. The cell contents, normally transparent, are changed into extremely minute pigment granules which fill the cells and give that characteristic color and smell which mark the disease. Moreover, minute drops of viscid offensive liquid come out on the surface. * From the cambium layer the fungus travels towards the interior of the stem through the medullary rays chiefly, and here I find those round bodies which in our ignorance we often call spores. The ducts which ascend the stem are often obstructed with similar bodies and aggregated pigment granules. This is all I know about the subject. I cannot venture to name the fungus." I have quoted this account at some length, for according to my observations it is the nearest approach to the solution of the cause of the difficulty founded upon direct investigation that had up to this time found its way into public print. Still it seems impossible to admit in full the correctness of the interpretations. What the round bodies called spores were, it is difficult to perceive. The dark color of blighted parts certainly does not come from pigment granules. The notice of the "offensive liquid” is a capital point, but this seems to have escaped careful examination. In 1876, Thomas Taylor of the Department of Agriculture, Washington, D. C., exhibited drawings at the Centennial Exposition showing 8 "the effects of the chemical changes which take place in the interior structure of the tree under the attacks of the fungus to which this disease is due." In 1877, the writer9 presented to the Illinois State Horticultural Society the results of microscopical observations, in the account of which occurs the first published notice of the minute moving Gardener's Monthly, 1875, p. 245. Report Department of Agriculture, 1876, p. 75. Transactions Illinois State Horticultural Society, 1877, p. 114. * * bodies always present in the portions of trees suffering from the malady of which we treat. I quote: "The cambium [a term here too loosely used] of the blighted branch, when trouble first shows itself, and for some days thereafter, is filled with very minute moving particles. Not unfrequently a thickish, brownish, sticky matter exudes from affected limbs, sometimes so abundant as to run down the surface or drop from the tree. This proves to be identical with that noticed in the cambium and unquestionably has the same origin. The sticky, half-fluid substance thus exuding is entirely made up of these minute oscillating particles." In a subsequent discussion in the same society I am credited with the following: 10"If we remove the bark of a newly affected limb and place a little of the mucilaginous fluid from the browned tissues under our microscope, the field is seen to be alive with moving atoms, known in a general way as bacteria. * A particle of this viscous fluid introduced upon the point of a knife into the bark of a healthy tree is in many cases followed by blight of the part, but with me not in every instance. * . If we look once more to the affected branch, we find the disease spreads more or less rapidly from the point of origin, and upon examination the moving microscopic things are discovered in advance of the discolored portions of the tissues, but not very far ahead an inch perhaps. [They are now known to advance several feet in certain cases, ahead of the black colored parts.] Does it not seem plausible that they cause the subsequently apparent change? It does to me, but this is the extent of my own faith; we should not say the conclusion is reached and the cause of the difficulty definitely ascertained. So far as I know, the idea is an entirely new one that bacteria cause disease in plants - though abundantly proved in the case of animals." -- - This is a very meagre sketch of the literature upon the subject, but nothing has been omitted which to my knowledge has special bearing upon the essential point of the present paper. After all the investigations that had been made and all that had been said a kind of ferment of itself— editors 11 were "obliged to reply," to quote from the American Agriculturist, "as we have many times in the past that the 'cause' of the blight is not known. It is supposed to be due to fungi, but this cause has not been 10 Transactions Illinois State Horticultural Society, 1878, p. 80. 11 American Agriculturist, Vol. 37, p. 356, 1878. |