These lichens are found on rocks, on the sea coast. The modes, of treating them for the manufacture of the different dyes is the same in principle, though varying slightly in detail. They are carefully cleaned and ground into a pulp with water, an ammoniacal liquor is from time to time added, and the ma.s.s constantly stirred in order to expose it as much as possible to the air. Peculiar substances existing in these plants are, during this process, so changed by the combined action of the atmosphere, water, and ammonia, as to generate the coloring matter, which, when perfect, is pressed out, and gypsum, chalk, or other substances, are then added, so as to give it the desired consistency; these are then prepared for the market under the forms of cudbear or litmus.

HENNA (_Lawsonia inermis_), is an important dye-stuff, and the distilled water of the flowers is used as a perfume. The Mahomedan women in India use the shoots for dyeing their nails red, and the same practice prevails in Arabia. In these countries the manes and tails of the horses are stained red in the same manner. The _Genista tomentosa_ yields red petals used in dyeing, and containing much tannic acid.

ORCHILLA WEED.--The fine purple color which the orchilla weed yields, is in use as an agent for coloring, staining, and dyeing. About 30,000 lbs. is obtained annually in the island of Teneriffe. 460 arrobas (or 115 cwt.) of orchilla were exported from the Canary Isles in 1833. In 1839, 6,494 cwts. paid duty, and 4,175 cwts. in 1840. The average imports of the three years ending with 1842, was 6,050 cwt. A little comes in from Barbary and the islands of the Archipelago.

Dr. W.L. Lindley, in a very interesting paper, read before the Botanical Society of London, in December, 1852, on the dyeing properties of the lichens, stated--

The subject of the _colorific_ and _coloring_ principles of the lichen has, within the last few years, attracted a due share of that attention which, has been increasingly devoted to organic chemistry.

Since 1830, Heeren, Kane, Schunck, Rochleder and Heldt, Knop, Stenhouse, Laurent and Gerhardt, have published valuable papers on these principles; but, here again, we have to regret the great discrepancy in the various results obtained, and there is therefore, here also, imperatively demanded re-investigation and correction before _any_ of the results already published can he implicitly relied upon, and before we can have safe data from which to generalise. I have no doubt that a great proportion of the obscurity overhanging this subject depends on the circ.u.mstance that many of the chemists, who have devoted attention to the color-educts and products of the lichens, were not themselves botanists, and have therefore probably, in some cases at least, a.n.a.lysed species under erroneous names, and also because their investigations have comprehended a much too limited number of species.

Their utility in the arts, and especially in dyeing--including the collection of a series of the commercial dye lichens, _i.e._, those used by the manufacturers of London, &c., in the making of orchil, cudbear, litmus, and other lichen dyes. While investigating the dyeing properties of the lichens, I made experiments, with a view to test their colorific power, on as many species as I could obtain in sufficient quant.i.ty, to render it at all useful to operate on--that number, however, being very limited (between forty and fifty).

Dr. Lindley adds, many parties may be able to aid his investigations, by furnishing information on their economic uses, and on their special applications in dyeing and other arts--(particularly on their employment, as dye agents, by the natives of Britain and other countries)--with specimens of the lichens so used, and their common names--specimens of fabrics dyed therewith--notes of the processes employed for the elimination of the dyes, &c. Parties resident in, or travelling through our western Highlands and Islands, the northern Highlands, Ireland, Wales, Norway, Iceland, and similar countries, are most likely to be able to afford this description of information--many native lichens being still used by the peasantry of these countries to dye their homespun yarn, &c.

He proceeded to treat--1. The vast importance of this humble tribe of plants in the grand economy of nature, as the pioneers and founders of _all_ vegetation. 2. Their importance to man and the lower animals, as furnishing various articles of food. 3. Their importance in medicine, and especially in its past history, at home and abroad. 4. Their importance in the useful and fine arts, and especially in the art of dyeing. 5. Their affinities and a.n.a.logies to other cryptogamic families, and to the Phanerogamia. 6. Their value as an element of the picturesque in nature; and, 7. Their typical significance.

He then adverted more especially to the subject of his communication, under the ten following heads:--

I. The colors of the Thallus and apothecia of Lichens--their causes, and the circ.u.mstances which modify and alter them.

II. History of the application of their coloring matters to the art of dyeing.

III. Chemical nature and general properties of these coloring matters.

IV. Tests and processes for estimating qualitatively, and quant.i.tatively the colorific powers of individual species--with their practical applications.

V. Processes of manufacture of the Lichen-dyes, on the large and small scale in different countries--with the principles on which they are founded.

VI. Nomenclature of the dye-Lichens, and of the Lichen-dyes.

VII. Botanical and commercial sources of the same.

VIII. Special applications of the Lichen-dyes in the arts.

IX. Commercial value of the dye-Lichens, and their products.

X. Geographical distribution of the dye-Lichens--with the effect of climate; situation, &c., on their colorific materials.

Of the four first sections of his paper, the following is a very short summary or synopsis:--

Under the first head, the author spoke of chlorophylle and various organic and inorganic substances, which enter into the formation of the colors of the thallus and apothecia of lichens, and of the modifications of these colors depending on various degrees of--1.

Exposure to air and light. 2. Temperature. 3. Moisture, &c. 4.

Atmospheric vicissitudes. 5. Season of the year. 6. Nature of the Gonidic reproduction (_i.e._, gemmation). 7. Nature of habitat. 8.

Organic decomposition. 9. Coalescence of parts, monstrosities, &c.

Under the second section, he traced historically the manufacture of Lichen-dyes, and the native use of Lichens as dye agents, among different nations, from the times of Theophrastus, Dioscorides, and Pliny, down to the present day, sketching briefly the ancient end modern history of orchil, cudbear, and litmus, and specifying the native use of lichen-dyes in different, countries of Europe, Asia, and America. He alluded more particularly to their application to the dyeing of yarns, &c., by the Scotch Highlanders, under the name of "_Crottles_." "The process of the manufacture of the various crottles, generally consisted in macerating the powdered lichen for two or three weeks, in stale urine, exposing the ma.s.s freely to the air by repeated stirring, and adding lime, salt, alum, or argillaceous and other substances, either to heighten the color or impart consistence. To such an extent did this custom at one time prevail, that, in several of our northern counties each farm and cottage had its tank or barrel of putrefying urine, a homely but perfectly efficient mode of generating the necessary amount of ammonia. In the county of Aberdeen, in particular, every homestead had its reservoir of "Graith,"[53] and the "Lit-pig,"[54] which stood by every fireside, was as familiar an article of furniture in the cots of the peasantry, as the "cuttie-stool," or the "meal girnel." So lately as 1841 (and I presume the practice continues to the present day), Mr. Edmonston stated that, of four or five native dyes, used by the Shetlanders to color cloth and yarns, two at least were furnished by lichens, viz., a _brown dye_ from _Parmelia saxatilis_, under the name of "Scrottyie," and a _red_ one from _Lecanora tartarea_, under that of "Korkalett." It is very probable, however, that steam and free trade have gradually dispelled this good old custom, even in the remoter corners of our island; machinery-made articles being now readily supplied, at a rate so extraordinarily cheap, as to render it absolutely expensive (as to time, if not also as to money) to prepare colors, even by a process so simple and inexpensive as that just mentioned."

Under the third head, he examined, in a general way, the chemistry of the colorific and coloring matters of the lichens and the results to which it has led, avoiding as much as possible the technicalities inseparable from such a subject, and giving a short _vise_ of the researches of Heeren, Kane, Rochleder, and Heldt, Stenhouse, Schunck, Laurent, and Gerhardt, and others. "Our untaught senses should undoubtedly lead us to expect the lichens, whose thallus exhibits the brightest tints, to yield the finest dyes, and these, too, of a color similar to that of the thallus, but experience teaches us that the beautiful reddish or purplish coloring-matters are producible in the greatest abundance by the very species from which we should least expect to derive any, viz., in those most devoid of external color. This, though at first sight very remarkable, is easily explicable, when we remember that, in most of the so-called dye-lichens, colorific principles exist in a colorless form, and only become converted into colored substances under a peculiar combination of circ.u.mstances.

"Some lichens contain coloring matters, ready formed, and these exhibit themselves in the tint of the thallus of the plants, _e.g._ chrysophanic [or parietinic] acid in _Parmelia parietina_, and vulpinic acid in _Evernia vulpina_. In other species we find principles, which, while in the plant, and unacted on by chemical re-agents, are colorless, but which, when the lichens are exposed to the combined influence of atmospheric air, water, and ammonia, yield colored substances. This series of colored products is usually comprehended more for convenience sake than on account of chemical ident.i.ty, under the generic term orceine."

The whole subject of the chemistry of these bodies is at present in a most unsatisfactory condition, demanding fresh investigation and research, in ill.u.s.tration of which, the author exhibited tables of the colorific and coloring principles, so far as they are at present known, showing their chemical formulae and the authority therefor, and various relative information. "It is highly probable that when the chemistry of the lichens has been more fully studied, and the whole subject of their color-educts and products better understood, we shall begin to reduce the present confused ma.s.s of complex substances, and find the same principles more extensively diffused through different lichen species." Dr. L. entered somewhat minutely on the chemical reactions of the better known colorific and coloring principles, and their derivatives, so far at least as these throw any light on the production and trans.m.u.tation of the red or purple colors extracted from what may be termed _par excellence_, the _dye-lichens_. After a few remarks on the chemical const.i.tution of orchil and litmus, as given by Kane, Gelis, Pereira, and others, he discussed the subject of decolorisation of weak infusions of orchil and litmus by exclusion of atmospheric air, and by various deoxidising agents, and the different theories as to the causation of this phenomenon. "I have repeatedly had occasion to notice that, when weak infusions of these substances are excluded for some time from atmospheric air, in a bottle, with a tightly fitting cork, they gradually lose color, but rapidly regain it on re-exposure. It is curious that both orchil and litmus are what are called transient or false colors, _i.e._, they slowly lose their bloom and tint by long exposure to the atmosphere; the coloring matter, therefore, appears to be decolorised both by exposure to, and exclusion from the air, phenomena apparently of very opposite characters. The cause of the latter phenomenon has never, so far as I am aware, been quite satisfactorily explained; but it has been variously supposed to be due:--

1. To the mere negation of oxygen.

2. To the development, in the liquids, of various substances, capable of exerting a decolorising influence on the coloring matter.

3. To deoxidation of the coloring matter by substances, which have a great tendency to become oxidised or peroxised; _e.g._ hydrogen, in the case of decolorisation by sulphuretted hydrogen, nascent hydrogen, and the protoxides of iron and tin, &c.

4. To the fixation of an additional amount of hydrogen in a new colorless body, formed by the union of the sulphuretted hydrogen or other substances with the coloring matter of the liquid. This view is chiefly supported by Kane, who says, "that precisely as the coloring matters combine with water, to form different shades of red-colored bodies--with ammonia to produce a series of bodies, which are blue and purple--so they combined with sulphuretted hydrogen to form colorless compounds in solution, which, if solid, very probably would be white." He supposes, in a word, that for every colored substance existing in orchil and litmus, there is a corresponding white one, producible by the action of sulphuretted hydrogen, &c.; and, in proof of this theory, he mentions having obtained from Azolitmine and Betaorceine colorless bodies, to which he gave the respective names of Leuco-litmine and Leuco-orceine.

The author then gave a short summary of Dr. Westring's experiments on the dyeing powers of the Swedish lichens, which he found might be conveniently divided into four cla.s.ses, according to the degree of heat employed in their maceration, viz.:--

1. Lichens, whose coloring matter was easily extractable by _cold_ water alone.

2. Those which required for the elimination of their coloring matter, maceration in _tepid_ water (_i.e._ below 258 degs. Swedish thermometer).

3. Those which required maceration in _warm_ water (_i.e._between 50 and 60 degs. Swedish thermometer).

4. Those requiring _boiling_ water alone, or with the aid of solvents.

"It must be admitted that our knowledge of the true nature of the colorofic and coloring principles of the lichens is, as yet, very imperfect and confused, and one great cause of the dubity and obscurity overhanging the subject, is the fact that different a.n.a.lysts have arrived at most opposite results, even in the examination of the same species. For instance, in _Rocella tinctoria_, which has, of all the dye-Lichens, been most frequently selected for a.n.a.lytical investigation, on account of its important product orchil, the discrepancies between the results obtained are very striking. In it Heeren discovered his _Erythrine_; Kane his _Erythriline_; Schunk his _Erythric acid_; and Stenhouse three different substances in as many varieties of the plant; all of these bodies differing more or less from each other in composition and properties (at least, if we are to a.s.sume, as correct, the descriptions given of them by their respective discoverers").

"I have already hinted that there is no ratio between the external and internal color or structure of a lichen, and the kind or amount of coloring matter it will be found to yield. It is exceedingly natural to suppose that such a ratio should exist; but, proceeding for some time on this supposition, I was frequently disappointed in my results--the most showy and brilliantly colored lichens often furnishing the dullest and most worthless colors. For instance, the bright yellow thallus of _Parmelia parietina_, and the beautiful scarlet apothecia of _Scyphophorus cocciferus_, instead of producing a rich yellow in the one case, and a deep crimson in the other, yielded, respectively, only dirty greenish-yellow and brownish colors. As a general rule I should almost be inclined to say that the finer the color of the thallus of any given lichen, the more is that lichen to be suspected of poverty in valuable coloring matters; and that, on the other hand, the palest pulverulent or crustaceous species, especially such as are saxicolous, may be expected to yield the most beautiful and valuable pigments (_e.g._ the Rocellas and Lecanoras). In such circ.u.mstances it is necessary to have some test, of easy applicability, of the kind and amount of colorific properties of any lichen, and this fortunately is readily attainable."

The fourth section of the paper was devoted to the consideration of the various tests of colorific power, which have been recommended by different authors. "Of these, the greater number proceed on the principle of developing the coloring matter by some alkali, in conjunction with the decomposing action of atmospheric oxygen and water; others are founded on the reaction between colorific principles of certain of the dye lichens and some of our ordinary chemical re-agents." The author noticed in particular--

1. Helot's test, } 2. Westring's tests, }qualitative.

3. Stenhouse's test, } 4. " quant.i.tative.

Helot's test consists in digesting the dried and powdered lichen or a few hours, at a temperature of 130 degs., in a weak solution of ammonia, sufficiently strong, however, to be tolerably pungent. One that is fit for the dyer will yield a rich violet red liquor.

Dr. Westring recommended simply macerating three or four drachms of the lichen in cool spring water, a.s.sisting, perhaps, the solvent action of the water by minute quant.i.ties of common salt, nitre, quicklime, sulphate of copper or iron, or similar re-agents. If these means failed, after a sufficient length of time had been allowed for the development of color, he digested a fresh portion of the pulverised lichen in water, containing small quant.i.ties of sal-ammoniac and quicklime [in the proportion of 25 parts of water, 1-10th lime, and 1-20th sal-ammoniac for every part of lichen], for a period varying from eight to fourteen days, and by this process, he says, he never failed to develop all the color which the plant was capable of yielding.

Dr. Stenhouse, of London, one of our latest and best authorities on the chemistry of the lichens, adds to an alcoholic infusion of the lichen, a solution of common bleaching powder (chloride of lime), whereby, if it contain certain colorific principles capable of developing, under the joint action of air, water, and ammonia, red coloring matters, a fugitive but distinct _blood-red color_ will be exhibited. The amount of this colorific matter may be estimated quant.i.tatively by noting the quant.i.ty of the chloride of lime solution required to destroy this blood-red color in different cases: or the same result may be obtained by macerating for a short period in milk of lime--filtering--precipitating the filtered liquor by acetic or muriatic acid--collecting this precipitate on a weighed filter--drying at ordinary temperatures and again weighing.

The author entered into a full a.n.a.lysis of these tests and processes--pointing out their respective advantages and disadvantages--and showing their practical value and applications.

He stated that he had made use of these, and various other tests, in upwards of 300 experiments, and the one which he employed to the greatest extent, because most uniformly applicable, was Helot's ammonia test. The following combination is that most favorable for the development of the coloring matter of the lichens--viz., the presence

1. Of _water_ as a solvent menstruum.

2. Of atmospheric _oxygen_.

3. Of _ammonia_, in the state of vapor or in solution, and 4. Of a moderate degree of _heat_;

And according as the proportion of these combining elements varies, so do the kind and amount of color educed by them. This combination is the foundation of all the processes for the manufacture of the lichen dyes throughout the world, however different these may appear to be in detail or results.

I believe it may come to be a matter of great commercial importance to discover, at home or abroad, some cheap and easily-procurable subst.i.tute for the _Roccellas_, which are gradually becoming scarce, and consequently valuable in European commerce, having sometimes fetched, in times of scarcity, no less than 1,000 per ton. No plants can be so easily collected and preserved as lichens--requiring merely to be cleaned, dried, pulverised, and packed; and if their bulk be an objection to transport, their whole colorific matter may be collected in the way I have already mentioned. Ascending to the verge of eternal snows, and descending to the ocean level--with a geographical diffusion that is co-extensive with the surface of our earth, it is difficult to say where lichens shall not be found. There are myriads of small rocky islets in the boundless ocean, and there are thousands of miles of barren rocky coast and sterile mountain range in every part of the world, which, though at present unfit to bear any of the higher members of the vegetable kingdom, are yet carpeted and adorned with a rich covering of lichens, and of those very species too, which I have already spoken of as prolific in colorific materials. I sincerely believe, therefore, that a more general attention to the very simple tests just enumerated, would ultimately result in a greatly extended use of the lichens as dye agents. What renders it very probable that efforts in this direction are likely to meet with success is the great similarity of species found all over the world.

It has been repeatedly noticed that the European species, which, of course, are best known, differ little from those of North America.

Dr. Robert Brown remarked the same fact with regard to New Holland species, and Humboldt also recognised the similarity in natives of the South American Andes. Of a large collection made by Professor Royle, in the Himalayas, Don p.r.o.nounced almost every one to be identical with European species. From examining the raw vegetable products, sent by different countries to the Great Exhibition of 1851, I am satisfied that, even now, there are many fields open for the establishment of an export trade in _Roccellas_ and other so-called orch.e.l.la weeds." I there saw specimens of good dye lichens from almost every part of the world, including our own young colonies; and as a single instance of their probable value, I may introduce here the copy of a note appended to a specimen of orch.e.l.la weed from the island of Socotra, contained in the Indian collection of that exhibition, "_abundant_, but _unknown_ as an article of use or commerce. Also abundant on the hills around (Aden) and _might_ be made an article of trade." Roccellas from this source are estimated as worth 190 to 380 per ton. I believe that a similar statement might be made with regard to the countless islands of the broad Atlantic and Pacific, which may, at some future period, perhaps not far distant, be found to be rich depots of orch.e.l.la weeds, just as some of them are, at present, rich fields of guano, and may, as such, become new nuclei of British commerce and enterprise. Even at home, in the immediate vicinity of Edinburgh, or, to restrict our limits still more narrowly, within the compa.s.s of Arthur's Seat, there are not a few very good dye-lichens, which require merely to be sc.r.a.ped with an old knife or similar instrument, from the rocks to which they adhere, and subjected to the ammonia process already mentioned. Of twelve specimens thus collected at random one morning, I found no less than three yielded beautiful purple-red colors, apparently as fine as orchil or cudbear, while the others furnished rich and dark tints of brownish-red, brown and olive-green.