The bacterium bodies probably give rise to the tough mucus in which they are involved, and the unorganized mass in which they are embedded in the vinegar plant may only differ in density from the more delicate material in which the same kind of bodies are enveloped when they form a pellicle on the surface of infusions, or adhere in a more or less globular shape. On this subject the remarks of Dr. Arlidge, in the first part of Pritchard's Infusoria, may be cited with advantage. He says, "When we come to examine an infusion rich in these organisms, numerous jelly-like colourless masses of different size and figure may be met with on the walls of the vessel, and on the surface of the fluid. These, when young, resemble small balls, from 1-1000" and less in diameter; but as they continue constantly to enlarge, they acquire a clustered outline, and exhibit themselves as colourless masses, and films of very considerable superficial dimensions and thickness, resembling soft palmellæ in consistence. Like these, they are composed of a transparent mucus, in which numberless punctate or linear corpuscles are embedded." Now, if we could make the mucus more dense and tough, multiply the "punctate or linear corpuscles" indefinitely, and introduce a sprinkle of larger cells analogous to those of the yeast, we should have a vinegar plant as its structure appears to me. The yeast plant is shown, as already stated, to be intimately connected, if not identical with, several vegetable forms to which distinct names have been assigned; but, both upon botanical and chemico-physiological grounds, it would be very interesting to ascertain to what extent that form of it known as the vinegar plant is associated with bacterium bodies. It is not enough that in one or two cases we find quantities of these bodies present when alcohol or saccharine matter is converted into vinegar-the question is, are they always present, and do they seem to be the particular agents by which the vinegarmaking is carried on. To ascertain this, the vessels of various sorts of vinegar works should be examined, and when the process is conducted by suffering a certain fluid to trickle over twigs or shavings, it should be ascertained whether bacterium bodies appear in quantity together with, or as a component part of the Mycoderma aceti, of which M. Pasteur speaks. Omitting those cases in which vinegar or acetic acid results from purely chemical processes, such as the destructive distillation of wood, or the influence of spongy platina, it appears to be obtained by the action of vegetable ferments on saccharine matter or alcohol, neither of which can be present in excess without stopping the process. Certain other substances in small quantities are also required to be present, or the growth of the organic bodies cannot proceed. In Germany, where alcohol is cheap, vinegar is made directly from it. Large VOL. IV.-NO. IV. S vats are fitted up with perforated shelves, on which a quantity of beech or deal shavings, first dried and soaked in strong vinegar, is placed. A mixture, consisting of one part of alcohol, sp. gr. 0-850, of six of water, and 1000th of honey, yeast, or wort, is allowed to trickle slowly through the shavings, while the temperature is raised to about 80 F. The acetification does not proceed rapidly until the process has been in operation for some days, that is to say, until the vinegar plant has had plenty of time to grow. Spongy platina will oxydize alcohol and generate vinegar as the vinegar plant does, although probably not precisely in the same way; but, however, alcohol becomes changed into acetic acid, Professor Miller considers that the formation of aldehyd always precedes the production of vinegar by an oxydizing process, and he gives the following formula as expressing what takes place when alcohol is thus transformed: C. He O2+ 20 = C1 H. O2+ 2 HO; and C. H. O+ 20 = Acetic acid. HỌ, C. H. O. When vinegar is obtained from a saccharine solution, the changes are more complicated; the cane-sugar is converted into grape-sugar, the grape-sugar into alcohol, and the alcohol into vinegar. Thus the vinegar plant appears to perform the double function of first alcoholizing and then acetifying the solution. Do the yeast-like cells accomplish one portion of this task, and the bacterium bodies the other? The mycoderm of wine does not in its ordinary state give rise to vinegar. Its own vital processes merely supply the means by which the changes incidental to vinous fermentation take place, but it occasionally happens that brewers are greatly teased by the acetous fermentation of their beer occuring after the alcoholic change has finished. I have heard of several instances this summer in which great annoyance has been experienced from this cause, and it would scem either that spores of the vinegar plant were diffused to a greater extent than usual, or that portions of yeast remaining in the beer had developed into the vinegar plant form. M. Pasteur's view of fermentation does not coincide with the common statement that the yeast plant merely separates sugar into carbonic acid and alcohol-at any rate he does not represent that as the entire process, because he tells us that when experiments were performed in close vessels containing, besides the fermenting liquid, a known quantity of air, it was found that the vinegar plant took oxygen from the air, and therewith converted the * Miller's Chemistry, vol. ii. p. 135. alcohol into acetic acid, and that the mycoderm of wine converted the alcohol into water and carbonic acid. Thus both act as oxydisers, and it is well known that if the vinegar plant be left in a fluid after it has transformed the sugar or alcohol into vinegar, it then burns up the vinegar, and leaves the housewife, or other manufacturer, who has neglected to remove it at the right period, only dirty water for her pains. M. Pasteur also tells us that the vinegar plant cannot acetify when it is submerged, while, as the German unterhefe yeast proves, the wine or beer fermentation can be excited by a yeast plant at the bottom of the fluid. These facts suggest inquiries into the action of different portions of a thick vinegar plant, of which one part is always under the fluid. It seems to the writer that Professor Graham's researches into dialysis afford a probable explanation of the actions of small plant cells in the cases adduced. Their delicate membranes give a preferential passage to one substance over another, and they may permit new combinations to be formed by allowing them the means of getting out of the way of those from which they were derived. They present oxygen to a compound, and if certain of its atoms choose to take it, they can escape with the new object of their chemical attachment. Thus the process bears some resemblance to the decompositions effected in water when that fluid allows the new resulting compound to fall as a precipitate, or escape as a gas. M. Béchamp states that acetic acid is one of the products of vinous fermentation, and the fact is accepted by M. Pasteur. M. Maumené disputed it, declaring that all well-made wines contained no acetic acid. This brought a rejoinder from M. Béchamp, to the effect that acetic acid is found even in the must of grapes. M. de Luca examined sixty-seven wines of Tuscany, and found acetic acid in all. M. Pasteur found that if a small quantity of vinegar was introduced when the Mycoderma vini was growing in an alcoholic liquid in contact with air, it disappeared, and he never obtained acetic acid from the growth of that plant in a liquid of this kind. These facts seem to show that the vinegar plant is present in all alcoholic fermentations, and exerts some action, although the chief and prevailing action is that of the Mycoderma vini, which is antagonistic to it, notwithstanding its analogous character. Here I leave the question for the present. I have brought forward certain facts which I think important, and many conjectures which may stimulate inquiry, if they are not of any other use. The subject is within the reach of thousands of microscopists who habitually read the INTELLECTUAL OBSERVER; and I shall be much obliged if any of them will favour me with any new information they may collect. THE DICRANUMS, OR FORK-MOSSES. BY M. G. CAMPBELL. ABOUT thirty species of Fork-moss are ascertained to be natives of the British isles. These, by strongly marked distinctions of foliage, naturally divide themselves into two groups, with the generic appellations of Dicranum and Fissidens. As six of the Dicranums are in fruit during the month of November, we will confine our attention to them for the present. They are named from Síxpavov, a forked instrument, in allusion to the cloven teeth of the genus, and are perennial plants, growing on rocks or on the ground, sometimes on the trunks of trees, in tufts more or less dense and extensive; the stems varying in height from a few lines to several inches; the smaller species not much unlike the Weissiæ; the larger, among which are some scarcely surpassed in size by any other of the acrocarpous division of mosses, in some instances bear considerable resemblance to the Trichostoma and Cynodontium. The leaves are usually somewhat lanceolate, spreading, or secund, i.e., all turned to one side, the reticulation variable, usually small, dot-like or roundish in the narrower part of the leaf, elongated, narrow, and often wavy lower down, at the marginal base considerably enlarged, quadrate, and tinged with colour more or less deeply. The calyptra cucullate, with a long beak; the lid conical at the base, with a long beak, slender oblique, and varying in length. The peristome single, consisting of sixteen equi-distant teeth, which are confluent at the base, and cloven half way or more into two unequal portions, the medial line being continued to the base with occasional perforations. They are also marked with transverse bars, prominent on the inside of the tooth, and surrounded externally with a somewhat rigid membrane of a red or orange colour. The spores are rather small and of a reddish brown tint. The most commonly met with is Dicranum heteromallum, or the Silky-leaved Fork-moss. It grows in extensive silky patches upon moist banks, the stems tufted, or matted together, simple or branched, with crowded secund leaves, somewhat bristle-shaped and slightly dentate at the apex, of a silky appearance and with a flattened nerve, which forms the chief part of the upper portion of the leaf, giving it the bristly appearance, and passing insensibly into the broader laminar substance of which the lower part of the leaf is composed. The capsule is cernuous, or sometimes sub-erect, obovate, gibbous, uniformly coloured of a reddish brown, with a somewhat, but never distinctly, strumose neck; the lid conical at the base, and tapering into a long beak, sometimes, but not always, with the reaping-hook-like curvature towards the extremity, as given in the illustration, which is a magnified representation of a specimen gathered from Ferny Hills, Nailsworth, where it seems to grow much more diminutively than in most other places, the usual height assigned to this moss being about an inch, while the specimens from Ferny Hills do not reach onefourth of that measurement. The seta or fruit-stalk is slender, of a pale yellowish colour, and rather long in proportion to the plant. When dry and empty the capsule is slightly and obliquely furrowed, by which character and by the pale seta Wilson says it may always be distinguished. In Dicranum pellucidum, or the Transparent Fork-moss, the leaves instead of being secund are squarrose, and variously bent. In form they are lanceolate from a slightly sheathing base, rather obtuse, entire, serrated or crenulate at the apex only, papillose on both sides, especially at the back and along the nerve, slightly undulated in the margin, keeled, and twisted or crisped when dry; and as D. heteromallum is found in patches of a deep, though bright green, D. pellucidum on the contrary grows in patches of a light green colour, from one to two inches high. The capsule is seated on a rather thick and wavy pale fruit-stalk; it is usually sub-cernuous, but in one variety erect, always roundish, shortly ovate or oblong, with thick firm walls of a reddish brown, becoming at length blackish, and destitute of a struma. The teeth of the peristome are variable both in form and markings, sometimes but very slightly cloven, and sometimes with prominent bars. The lid is large, conical at the base, with a longer or shorter oblique beak, always much thicker than in heteromallum. D. pellucidum grows on wet rocks and stones in shady rivulets, and loves the spray of cascades. Dicranum Schreberi, or Schreber's Fork-moss, grows also in light green patches, but the stems are only from half an inch to one inch in height. It is also found by rivulets or ditches, on sandy or clayey soil, but is regarded as rare. The inflorescence of all three is dioicus, the barren flower being terminal on a separate individual. The leaves of D. Schreberi are widely spreading, and flexuose; from a broad sheating base they suddenly contract into a narrowly lanceolate, or lanceolato-subulate form, denticulate in the margin near the apex, with a nerve ceasing below the |