"The overlying deposits are generally a foot or two of mud, the same thickness of clay, a layer of peat sometimes intervening, and below the clay shell-marl containing everywhere the relics of fresh-water testacea of existing species; some of them perfect, others decomposing. Sir Chas. Lyell, in his geological tour through the State of New York, found at Genessee, the bones of the mastodon in a bed of shell-marl below the peat, corresponding, he remarks, with the situation of the fossil elks of Ireland, generally considered to have been buried in bogmud or peat swamps, but which, in fact, lie in a stratum of shell-marl."

It seems probable that the enormous quantities of moa bones found in the turbary area at Glenmark, New Zealand, afford some grounds for questioning the destructive influence of vegetable acids. According to Dr. Von Haast, a large swampy tract in Glenmark, covering a depressed region and partaking of the mingled characters of an estuarine and lacustrine basin, contains an incredible number of the skeletons of these great birds. The bones occur here in separated patches or nests, and the impression, made by their distribution, is that of a sudden flight of groups of the birds over this marshy delta which has sunk in places beneath them, and thus entrapped them in constantly increasing numbers. Bones of twenty or thirty individuals, of all sizes and ages, and lying closely packed in spots about five or six feet in diameter, are found with no bones near them, as if, at particular points, the birds had disappeared, one after another, in the enveloping mass of vegetable débris and soft mud. Evidences here are everwhere plentiful of successive freshets by which accumulations of trees, seeds, stems and drift timber have been formed, which, with the growth of bog plants, created a deep vegetable blanket in which the moa bones are immersed. Four to seven feet of pure black peat are succeeded by two to three feet of more impure peat, in which the bird bones are more commonly laid, and under these a hard clay bottom completes the section. It

Geology of Canterbury and Westland, New Zealand, J. Von Haast. See also Ann. & Mag. Nat. Hist., Aug., 1844, Rev. W. Colenso; Transac. New Zealand Inst., Vols. IV, VI, J. Von Haast.

would seem reasonable to expect a plentiful production of humic acid and its allied compounds under these circumstances, and if, as Julien asserts, these acids attack the phosphates of alkaline earths (phosphates of alumina lime and magnesia), the preservation of the moa bones appears either exceptional or contradictory.

In this connection it must be remembered that in all such vegetable infusions a considerable amount of tannin must accumulate, and its astringent action upon the gelatine of bone has a tendency to protect the bone along the interior walls of its cavities and canals. Lyell is at some pains to illustrate, in his Principles, Vol. II, pp. 508–510, the preservative properties of peat, but these illustrations relate more to its antiseptic properties for the preservation of animal tissues. Thus, in a peat-moss in the Isle of Axholm, Lincolnshire, Scotland, a body of a woman was preserved six feet below the surface; bodies of two persons in Derbyshire, England, were kept quite uninjured in moist peat, and pigs were found intact in a peaty soil near Dubuerton, Somersetshire.

There is also a possibly protective action exercised at times by the organic acids themselves when they concentrate upon a nucleus of bony fragments, precipitates of iron oxide or amorphous silica. This is done by their reduction of iron salts forming organic compounds, or by combination with silica in the dissolved silica of the infiltrating streams. The iron is liberated from solution by oxydation and the silica by decomposition, and both iron oxide and soft silica may be thus introduced into the interstices of the bone and serve as agents of induration. It is said by Von Haast that the moa bone layer at Glenmark is somewhat reddish. This may be attributed to ferruginous encrustations. Again, the action of organic acids on such material as the harder class of bone must be somewhat limited by dilution, and the constant percolation of water from surface water-courses and rains must considerably neutralize the corrosive power of the readily dissolved vegetable fluids. Again, these vegetable fluids are quite liberally employed in making defensive combinations with the mineral matter brought to them in complete solution or mechanically

suspended in the streams passing over and through marshes, swamps, bogs and deltas, and are so divested of any destructive power upon bone. And in any case, the elaboration of these acid products which we are considering would be partial or completely suspended at such depths as are usually given for the repositories of vertebrate remains. Yet, however diverted or minimized may be the action of organic acids and carbonated water upon bone, there can be little doubt that it is considerable, and an important means in many cases of imparting to them much fragility or of entirely disintegrating them.

(To be Continued.)

THE BACTERIAL DISEASES OF PLANTS:

A CRITICAL REVIEW OF THE PRESENT STATE OF OUR KNOWLEDGE.

BY ERWIN F. SMITH.

(Continued from p. 804)
IV.

II. THE HYACINTH (HYACINTHUS ORIENTALIS).

(II) THE ORGANISM: Bacillus hyacinthi (Wakk.) Trev. (1883). 1. Pathogenesis:

(A) Yes.

(B) Yes (?). The poured plate method was not then in general use. Inoculations were made directly from diseased plants into sterile nutrient fluids, or into tubes of nutrient gelatin, and the resulting cultures may not always have been pure ones, although the writer's own experience has shown conclusively, in case of melon wilt-a somewhat similar disease-that it is often possible to obtain pure cultures in this way, if the culture

media is sterile to begin with and the necessary precautions are taken to exclude surface contaminations and air-borne germs. His experiments were, however, checked and controlled by means of poured plates, whereas Dr. Wakker had advantage of no such exact method. Nevertheless, he seems to have worked with great care, and states positively that although the bacteria were often transferred from diseased plants to the culture media, and also from one tube of media to another, the results were always the same, which could scarcely have been the case were intruding organisms present.

(C) Yes (?). Infections with artificial cultures had not been secured up to March, 1895, and do not appear to have ever been very numerous or very successful. The only experiment which seems to come properly under this head was begun March 4, 1886. The inoculations were made from a liquefied gelatin culture, the fluid being inserted into fresh cuts on the scapes of several (more than five) varieties of hyacinths. In a week all of the scapes began to dry out and soften, from the summit downward; and fifteen days later the greater part of each one was either entirely dry, or soft and flacid. An earlier effort to infect from a bouillon culture failed (Verslag, 1884).

(D) Yes; in part. On microscopic examination of the scapes mentioned under C it was easy to determine in them the existence of the yellow disease; but this did not extend into the bulbs. "These experiments [referring to those mentioned under I (5) as well as this one] were repeated and varied with, in general, concordant results."

Conclusion.-Pathogenic nature rendered probable.

Remarks. As will be seen later on, this organism was imperfectly described, and any bacteriologist having opportunity to repeat and extend Dr. Wakker's experiments should by all means embrace it.

2. Morphology:

(1) Shape, size, etc.—The bacteria which Dr. Wakker regards as the cause of this disease are represented on his Plate I, Figs. 1-8 (34). They are two to four times as long as broad, with an ordinary length of about 2.5 μ. Their form is therefore more or less that of a cylinder, but with rounded ends. They are said to agree tolerably well in size and shape with Bacterium Termo. The organism was described as Bacterium Hyacinthi in 1883, but was placed under Bacillus by Trevisan in 1889. When these bacteria have been in a nutrient liquid for some time a certain number become longer than they were, and now measure 4, while the ordinary length is only 2.5. Later on, as the nutrient matters of the liquid are becoming exhausted, the bacteria diminish in size more and more, and gather into motionless groups, which often have circular outlines and which grow by the accession of new individuals, while the motile bacteria become less and less numerous. Bacteria from the dry slime were found to be only about half the ordinary size, but on placing them in nutrient fluids they resumed their normal size. Examinations were made in hanging drops of nutrient fluid.

(2) Capsule.-No mention of any capsule.

(3) Flagella.-No mention of flagella. The organism is said to be actively motile in culture fluids. Even those kept for some time in a dry state are said to have acquired motility on placing them in nutrient fluids. In the yellow, viscid slime, as taken from the plant, they are not motile; but motility begins as soon as this is diluted with a per cent. salt solution, or with a suitable nutrient fluid. "After a short time all is life and motion; the bacteria, in the form of straight but very flexible rods, are to be seen moving about actively; individuals in repose are rare. Among the undivided bacteria there are many which are in process of division, and which then show two individuals moving together; these, however, soon separate to continue an independent existence." It will probably be found that the organism is also motile in the plant in early stages of the disease, i. e., before it has multiplied to such an extent as to fill the vessels. Dr. Wakker himself says: "It is evident that