Chapter X: Economic and Technical

A. LICHENS AS FOOD.

_a._ FOOD FOR INSECTS, ETC. Some of the earlier botanists made careful observations on the important place occupied by lichens in nature as affording food to many small animals. In 1791 Jacques Brez[1226] wrote his _Flore des Insectophyles_, and in the list of food-plants he includes seven species of lichens. The “insects” that frequented these lichens were species of the genera _Acarus_ (mites) and _Phalena_ (moths). A few years later Persoon[1227] noted that lichens formed the main food supply of many insects, slugs, etc. Zukal[1228], quoting from Otto Wilde (_Die Pflanzen und Raupen Deutschlands_, Berlin, 1860), gives a list of caterpillars that are known to feed on and destroy lichens.

A very considerable number of small creatures feed eagerly on lichens, and traces of their depredations are constantly to be seen in the empty fruit discs, and in the cortices eaten away in patches so as to expose the white medulla. It has been argued by Zukal[1229] that the great formation of acid substances in lichens is for shielding them against the attacks of animals; Zopf[1230] on the contrary insists that these substances afford the plants no real protection. He made a series of experiments with snails, feeding them with slices of potato smeared with pure lichen acids. Many snails ate the slices with great readiness even when covered with bitter acids such as cetraric, or with those which are poisonous for other animals such as rhizocarpic and pinastrinic. The only acid they refused was vulpinic, which is said to be poisonous for vertebrates. The crystals of the acids passed unchanged through the alimentary canal of the snails, and were found in masses in the excreta. They were undissolved, but, enclosed in slime, their sharp edges did no damage to the digestive tract.

Stahl[1231] however upholds Zukal’s theory of the protective function of lichen acids against the attacks of small animals. Some few snails, caterpillars, etc., that are omnivorous feeders consume most lichens with impunity, and the bitter taste seems to attract rather than repel them; but many others he contends are certainly prevented from eating lichens by the presence of the acids. He proved this by soaking portions of the thalli of certain bitter species for about twenty-four hours in a one per cent. soda solution, which was sufficiently strong to extract the acids. He found that these treated specimens were in most cases preferred to fresh portions that had been simply moistened with water.

Even the omnivorous snail, _Helix hortensis_, was several times observed to touch the fresh thallus and then creep away, while it ate continuously the soda-washed portion as soon as it came into contact with it. Calcium Oxalate, on the other hand, formed no protection; omnivorous feeders ate indifferently calcicolous lichens such as _Aspicilia calcarea_ and _Lecanora saxicola_, whether treated with soda or not, but would only accept lichens with acid contents, such as _Parmelia caperata_, _Evernia prunastri_, etc., after they had been duly soaked.

Experiments were also made with wood-lice (_Oniscus murarius_), and with earwigs (_Forficula auricularia_), and the result was the same: they would only eat bitter lichens after the acids had been extracted by the soda method. Stahl therefore concludes that acids must be regarded as eminently adapted to protect lichens which otherwise, owing to their slowness of growth, would scarcely escape extinction.

The gelatinous Collemaceae, as also _Nostoc_, the alga with which these are associated, are unharmed by snails, etc., on account of their slippery consistency when moist, which prevents the creatures from getting a foothold on the thallus. These lichens however do not contain acids, and if, when dry, they are reduced to powder and then moistened, they are eagerly eaten both by snails and by wood-lice. _Peltigera canina_, on account of a disagreeable odour it acquires on being chewed, is avoided to a certain extent, but even so it is frequently found with much of the thallus eaten away.

Hue[1232] in his study of Antarctic lichens, comments on the abundance and perfect development of the lichens, especially the crustaceous species, which cover every inch of rock surface. He ascribes this to the absence of snails and insects which in other regions so seriously interfere with the normal and continuous growth of these plants.

Snails do not eat lichens when they are dry and hard, but on damp or dewy nights, and on rainy days, all kinds, both large and small, come out of their shells and devour the lichen thalli softened by moisture. Large slugs (_Limax_) have been seen devouring with great satisfaction _Pertusaria faginea_, a bitter crustaceous lichen. The same _Limax_ species eats many different lichens, some of them containing very bitter substances. Zopf[1233] observed that _Helix cingulata_ ate ten different lichens, containing as many different kinds of acid.

Other creatures such as mites, wood-lice, and the caterpillars of many butterflies live on lichens, though, with the exception of the caterpillars, they eat them only when moist. Very frequently the apothecial discs and the soredia are taken first as being evidently the choicest portions. All lichens are, however, not equally palatable. Bitter[1234] observed that the insect _Psocus_ (_Orthoptera_) had a distinct preference for certain species, and restricted its attention to them probably because of their chemical constitution. He noted that in a large spreading thallus of _Graphis elegans_ on holly, irregular bare spots appeared, due to the ravages of insects—probably _Psocus_. In other places, the thallus alone had been consumed, leaving the rather hard black fruits (lirellae) untouched. In time the thallus of _Thelotrema lepadinum_, also a crustaceous lichen, invaded the naked areas, and surrounded the _Graphis_ lirellae. The new comer was not to the taste of the insects and was left untouched.

Petch[1235] says that lichens form the staple food of _Termes monoceros_, the black termite of Ceylon. These ants really prefer algae, but as the supply is limited they fall back on lichens, though they only consume those of a particular type, or at a particular stage of development. Those with a tough smooth cortex are avoided, preference being given to thalli with a loose powdery surface. At the feeding ground the ants congregate on the suitable lichens. With their mandibles they scrape off small fragments of the thallus which they form into balls, varying in size from 1·5 mm. to 2·5 mm. in diameter. The workers then convey these to the nests in their mandibles. It would seem that they carry about these balls of food, and allow the ants busy in the nest to nibble off portions. Lichen balls are not used by termites as fungi are, for “gardens.”

Other observations have been made by Paulson and Thompson[1236] in their study of Epping Forest lichens: “Mites of the family Oribatidae must be reckoned among the chief foes of these plants upon which they feed, seeming to have a special predilection for the ripe fruits. We have had excellent specimens of _Physcia parietina_ spoiled by hidden mites of this family, which have eaten out the contents of the mature apothecia after the lichens have been gathered. One can sometimes see small flocks of the mites browsing upon the thallus of tree-dwelling lichens, like cattle in a meadow.” The Oribatidae, sometimes called beetle-mites, a family of Acarinae, are minute creatures familiar to microscopists. They live chiefly on or about mosses, but Michael[1237] is of opinion that a large number frequent these plants for the fungi and lichens which grow in and about the mosses. In Michael’s _Monograph of British Oribatidae_, four species are mentioned as true lichen-lovers, _Leiosoma palmicinetum_ found on _Peltigera canina_ and allied species; _Cepteus ocellatus_ and _Oribata parmeliae_ which live on _Physciae_, the latter exclusively on _Physcia_ (_Xanthoria_) _parietina_; and _Scutovertes maculatus_ which confines itself to lichens by the sea-shore. Another species, _Notaspis lucorum_, frequents maritime lichens, but it is also found on other substrata; while _Tegeocranus labyrinthicus_, though usually a lichen-eating species, lives either on mosses or on lichens on walls. Zopf[1238] reckoned twenty-nine species of lichens, mostly the larger foliose and fruticose kinds, that were eaten by mites. Lesdain[1239] in his observations on mite action notes that frequently the thallus round the base of the perithecia of _Verrucaria_ sp. was eaten clean away, leaving the perithecia solitary and extremely difficult to determine.

J. A. Wheldon[1240] found the eggs of a species of mite, _Tetranychus lapidus_, attached to the fruits of _Verrucaria calciseda_, _Lecidea immersa_ and _L. Metzleri_, calcicolous lichens of which the thallus not only burrows deep down into the limestone, but the fruits form in shallow excavated pits (Fig. 126). The eggs of this stone mite are found fairly frequently on exposed limestone rocks, bare of vegetation, except for a few crustaceous lichens. “There is usually a single egg, rarely two, in each pit apparently attached to the old lichen apothecium. The eggs are very attractive objects under a lens; they measure ·5 mm. in diameter, and are disc-like with a central circular depression from which numerous ridges radiate to the circumference, like the spokes of a wheel. When fresh, they have a white pearly lustre, becoming chalk-white when dry and old.” Wheldon’s observations were made in the Carnforth and Silverdale district of West Lancashire.

A minute organism, _Hymenobolina parasitica_[1241], first described by Zukal and doubtfully grouped among the mycetozoa, feeds, in the plasmodium stage, on living lichens. The parasitic habit is unlike that of true mycetozoa. It has recently been recorded from Aberdeenshire.

_b._ INSECT MIMICRY OF LICHENS. Paulson and Thompson[1242] give instances of moth caterpillars, which not only feed on lichens, but which take on the coloration of the lichens they affect, either in the larval or in the perfect moth stage. “One of the most remarkable examples of this protective resemblance to lichens is that of the larva of the geometrid moth, _Cleora lichenaria_, which feeds upon foliose lichens growing upon tree-trunks and palings, and being of a green-grey hue, and possessed of two little humps on many of their body-segments, they so exactly resemble the lichens in colour and appearance as to be extremely difficult of detection.” Several instances are recorded of moths that resemble the lichens on which they settle: perfect examples of such similarity are exhibited at the Natural History Museum, South Kensington, where _Teras literana_, _Moma orion_, and other moths are shown at rest on lichen-covered bark from which they can hardly be distinguished.

Another curious instance of suggested mimicry is recorded by G.E. Stone[1243]. He spotted a number of bodies on the bark of some sickly elms in Massachusetts. They were about 1/8 of an inch in diameter “with a dark centre and a drab foliaceous margin.” They were principally lodged in the crevices of the bark and Stone collected them under the impression that they were the apothecia of a lichen most nearly resembling those of _Physcia hypoleuca_. Some of the bodies were even attached to the thallus of a species of _Physcia_; others were on the naked bark and had every appearance of lichen fruits. Only closer examination proved their insect nature, and they were identified as belonging to a species _Gossypina Ulmi_, an elm-leaf beetle common in Europe where it causes a disease of the tree. It had been imported into the United States and had attacked American elms.

It is stated by Tutt[1244] that the larvae of many of the Psychides (_Lepidoptera_) live on the lichens of trees and walls, such as _Candelaria concolor_, _Xanthoria parietina_, _Physcia pulverulenta_ and _Buellia canescens_, and that their larvae pupate on their feeding grounds. Each species makes a “case” peculiar to itself, but those of the lower families are usually covered externally with grains of sand, scraps of lichens, etc. The “case” of _Narcyria monilifera_, for instance, is somewhat raised on a flat base and is obscured with particles of sand and yellow lichen, giving the whole a yellow appearance. That of _Luffia lapidella_ is roughly conical and is held up at an angle of 30° to 45° when the larva moves. The “cases” of _Bacotia sepium_ are always upright; they measure about 5·5 mm. in height and 2·75 mm. in width and present a hoary appearance from the minute particles of lichen with which they are covered, so that the structure is not unlike the podetium of a _Cladonia_.

_c._ FOOD FOR THE HIGHER ANIMALS. It has been affirmed, especially by Henneguy, that many lichens, if deprived of the bitter principle they contain, by soaking in water, or with the addition of sodium or potassium carbonate, might be used with advantage as fodder for animals. He cites as examples of such, _Lobaria pulmonaria_, _Evernia prunastri_, _Ramalina fraxinea_, _R. farinacea_, and _R. fastigiata_, all of which grow abundantly on trees, and owe their nutritive quality to the presence of lichenin, a carbohydrate allied to starch.

_Cladonia rangiferina_ (Fig. 127), the well-known “reindeer moss,” is, however, the lichen of most economic importance, as food for reindeer, cattle, etc. It is a social plant and forms dense tufts and swards of slender, much branched, hollow stalks of a greenish-grey colour which may reach a height of twelve inches or even more; the stalks decay slowly at the base as they increase at the apex, so that very great length is never attained. In normal conditions they neither wither nor die, and growth continues indefinitely. It is comparatively rare in the northern or hilly regions of the British Isles, and is frequently confused with the somewhat smaller species _Cl. sylvatica_ which is very common on our moorlands, a species which Zopf[1245] tells us reindeer absolutely refuse to eat.

The true reindeer moss is abundant in northern countries, more especially in forest regions[1246] and in valleys between the tundra hills which are more or less sheltered from the high winds; it is independent of the substratum and flourishes equally on barren sand and on wet turf; but grows especially well on soil devastated by fire. For long periods it may be covered with snow without injury and the reindeer are accustomed to dig down with horns and hoofs in order to reach their favourite food. Though always considered as peculiarly “reindeer” moss, deer, roebuck and other wild animals, such as Lemming rats[1247], feed on it largely during the winter. In some northern districts it is collected and stored as fodder for domestic cattle; hot water is poured over it and it is then mixed with straw and sprinkled with a little salt. Johnson[1248] has reported that the richness of the milk yielded by the small cows of Northern Scandinavia is attributed by some to their feeding in great measure on the “reindeer moss.”

When _Cladonia rangiferina_ is scarce, a few other lichens[1249] are made use of, _Alectoria jubata_, a brownish-black filamentous tree-lichen being one of the most frequent substitutes. _Stereocaulon paschale_, which grows in large dense tufts on the ground in mountainous regions, is also eaten by reindeer and other animals; and Iceland moss, _Cetraria islandica_, is stored up in large quantities by the Icelanders and used as fodder. Willemet[1250] reports it as good for horses, oxen, cows and pigs.

It is interesting to recall a discovery of prehistoric remains at the Abbey of Schussenried on the Lake of Constance and described by F. Keller[1251]: under successive beds of peat and crumbly tufa, there was found a layer, 3 feet thick, containing flints, horns of reindeer and bones of various animals, and, along with these, masses of reindeer moss; a sufficient proof of its antiquity as a fodder-plant.

_d._ FOOD FOR MAN. Lichens contain no true starch nor cellulose, but the lichenin present in the cell-walls of the hyphae has long been utilized as a food substance. It is peculiarly abundant in _Cetraria islandica_ (Fig. 128), which grows in northern countries, covering great stretches of ground with its upright strap-shaped branching fronds of varying shades of brown. In more southern lands it is to be found on high hills or on upland moors, but in much smaller quantities. Commercial “Iceland moss” is supplied from Sweden, Norway or Iceland. In the last-named country the inhabitants harvest the lichen preferably from bare stony soil where there is no admixture of other vegetation. They revisit the locality at intervals of three years, the time required for the lichen to grow to a profitable size; and they select the wet season for the ingathering of the plants as they are more easily detached when they are wet. If the weather should be dry, they collect it during the night. When gathered it is cleansed from foreign matter and washed in water to remove as much as possible of the bitter principle. It is then dried and reduced to powder. When required, the powder is put to macerate in water for 24 hours, or it is soaked in a weak solution of soda or of carbonate of potassium, by which means the bitter cetraric acid is nearly all eliminated. When boiled[1252] it yields a jelly which forms the basis of various light and easily digested soups or of other delicacies prepared by boiling in milk, which have been proved to be valuable for dyspeptics or sufferers from chest diseases. The northern nations also make the powder into bread, porridge or gruel. Johnson[1253] states in his account of “Useful Plants” that considerable quantities of Iceland moss were formerly employed in the manufacture of sea biscuit, and that ship’s bread mixed with it was said to be less liable to the attacks of weevil than when made from wheat flour only.

An examination of the real food value of the mucilaginous extract from “Iceland moss” has been made by several workers. Church[1254] states that for one part of flesh formers, there are eight parts of heat-givers reckoned as starch. Brown[1255] isolated the two carbohydrates, lichenin and isolichenin. The former, a jelly which yields on hydrolysis a large quantity of a reducing sugar, dextrose, ferments with yeast and gives no phloroglucin reaction; it is unaffected by digestion and probably does not form glycogen. Iso-lichenin is much less abundant and resembles soluble starch, but on digestion yields only dextrins—no sugar. It may be concluded, judging from the chemical nature of the mucilage, from the resistance of its constituents to digestion and from the small amount present in the jelly, that its nutritive value is practically nil[1256].

It has been stated that “reindeer moss” in times of food scarcity is powdered and mixed with “Iceland moss” and rye to make bread in North Finland. Johnson confirms this and cites the evidence of a Dr Clarke that: “to our surprise we found we might eat of it with as much ease as of the heart of a fine lettuce. It tasted like wheat-bran, but after swallowing it, there remained in the throat and upon the palate a gentle heat, or sense of burning, as if a small quantity of pepper had been mixed with the lichen.”

The Egyptians[1257] have used _Evernia prunastri_, more rarely _E. furfuracea_, in baking. In the eighteenth century fermentative agents such as yeast were unknown to them, and these lichens, which were imported from more northern lands, were soaked in water for two hours and the solution then mixed with the flour to give a much appreciated flavour to the unleavened bread.

In India[1258] a species of _Parmelia_ (near to _P. perlata_) known in the Telegu language as “rathapu” or rock-flower has been used as a food, generally prepared as a curry, by the natives in the Bellary district (Madras Presidency), and is esteemed as a delicacy. It is also used medicinally. The collecting of rathapu is carried on during the hot weather in April and May, and forms a profitable business.

A note has been published by Calkins[1259], on the authority of a correspondent in Japan, that large quantities of _Endocarpon_ (_Dermatocarpon_) _miniatum_ (Fig. 56) are collected in the mountains of that country for culinary purposes, and largely exported to China as an article of luxury. The local name is “iwataka,” meaning stone-mushroom. Properly prepared it resembles tripe. It is possibly the same lichen under a different name, _Gyrophora esculenta_, which is described by Manabu Miyoshi[1260] as of great food value in Japan where it is known as “iwatake.” It is a greyish-brown leathery “monophyllous” plant of somewhat circular outline and fairly large size, measuring 3 to 13 cm. across. Fertile specimens are rare, and are smaller than the sterile. It grows generally on the steep declivities of damp granitic rocks and is common in various districts of Japan, being especially abundant on such mountains as Kiso, Nikko, Kimano, etc. The face of the precipices is often thickly covered with the lichen growth. The inhabitants collect the plants in large quantities. They dry them and send them to the towns, where they are sold in all vegetable stores; some are even exported to other countries. These lichens are not bitter to the taste, nor are they irritating as are other species of the genus. They are on the contrary quite harmless and are much relished by the Japanese on account of their agreeable flavour, in spite of their being somewhat indigestible. Though only determined scientifically in recent times, this edible lichen has long been known, and the risks attending its collection have frequently been described in Old Chinese and Japanese writings.

Other species of _Gyrophora_ including _G. polyrhiza_ (Fig. 129) and _Umbilicaria_, black leathery lichens which grow on rocks in northern regions, have also been used as food. They are the “Tripe de Roche” or Rock Tripe of Arctic regions, a name given to the plants by Canadian fur-hunters. They have been eaten by travellers and others in desperate straits for food; but though to a certain extent nutritious, they are bitter and nauseous, and cause severe internal irritation if the bitter acids are not first extracted by boiling or soaking.

Of more historical interest is the desert lichen _Lecanora esculenta_, supposed to be the manna[1261] of the Israelites, and still called “bread from heaven.” Eversmann[1262] wrote an account of its occurrence and qualities, and fuller information was given by Berkeley[1263]: when mixed with meal to a third of its weight it is made into bread and eaten by the desert tribes. It grows abundantly in North Africa and in many parts of Western Asia, on the rocks or on soil. It is easily broken off and driven into heaps by the wind; and has been reported as covering the soil to a depth of 15 cm. to 20 cm. with irregular contorted lumps varying in size from a pea to a small nut (Fig. 130). Externally these are clear brown or whitish; the interior is white, and consists of branching interlaced hyphae, with masses of calcium oxalate crystals, averaging about 60 per cent. or more of the whole substance.

A still more exhaustive account is given by Visiani[1264], who quotes the experience of a certain General Jussuf, who had tested its value in the Sahara as food for his soldiers. When bread was made from the lichen alone it was friable and without consistency; when mixed with a tenth portion of meal it was similar to the soldiers’ ordinary bread, and had something of the same taste. The General also gave it as fodder to the horses, some of them being nourished with the lichen and a mixture of barley for three weeks without showing any ill effects. It is also said that camels, gazelles and other quadrupeds eat it with advantage, though it is in any case a very defective food.

A remarkable deposit of the lichen occurred in recent times in Mesopotamia during a violent storm of hail. After the hail had melted, the ground was seen to be covered, and specimens were sent to Errera[1265] for examination. He identified it as _Lecanora esculenta_. In his opinion two kinds of manna are alluded to in the Bible: in one case (Exodus xvi.) it is the sweet gum exuded from the tamarisk that is described; the other kind (Numbers xi.), he thinks, plainly refers to the lichen. He considers that its nutritive value must be very low, and it can only be valued as food in times of famine.

B. LICHENS AS MEDICINE

_a._ ANCIENT REMEDIES. An interesting note has been published by Müller-Argau[1266] which seems to trace back the medicinal use of lichens to a very remote age. He tells us that Dr Schweinfurth, the distinguished traveller, who made a journey through the valley of the Nile in 1864, sent to him from Cairo a piece of lichen thallus found in a vase along with berries of _Juniperus excelsa_ and of _Sapindus_, with some other undetermined seeds. The vase dated from the 18th Dynasty (1700 to 1600 B.C.), and the plants contained in it must thus have lain undisturbed over 3000 years. The broken pieces of the lichen thallus were fairly well preserved; they were extremely soft and yellowish-white and almost entirely decorticate, but on the under surfaces there remained a few black patches, which, on microscopical examination, enabled Müller to identify them as scraps of _Evernia furfuracea_. This lichen does not grow in Egypt, but it is still sold there along with _Cetraria islandica_ and some other lichens as foreign drugs. Dr Schweinfurth considered his discovery important as proving the use of foreign remedies by the ancient Egyptians.

_b._ DOCTRINE OF “SIGNATURES.” In the fifteenth century A.D. there was in the study and treatment of disease a constant attempt to follow the guidance of nature. It was believed that Providence had scattered here and there on plants “signatures,” or resemblances more or less vague to parts of the human body, or to the diseases to which man is subject, thus indicating the appropriate specific.

Lichens among other plants in which any “signature” could be detected or imagined were therefore constantly prescribed: the long filaments of _Usnea barbata_ were used to strengthen the hair; _Lobaria pulmonaria_, the true lung-wort, with its pitted reticulate surface (Fig. 72), was marked as a suitable remedy for lung troubles; _Xanthoria parietina_ being a yellow lichen was supposed to cure jaundice, and _Peltigera aphthosa_, the thallus of which is dotted with small wart-like tubercles[1267], was recommended for children who suffered from the “thrush” eruption.

The doctrine reached the height of absurdity in the extravagant value set on a lichen found growing on human skulls, “Muscus cranii humani” or “Muscus ex cranio humano.” There are a number of lichens that grow indifferently on a variety of substances, and not infrequently on bones lying in the open. This skull lichen[1268], _Parmelia saxatilis_ (Fig. 131) or some other, was supposed to be worth its weight in gold as a cure for epilepsy. Parkinson[1269] tells us in all confidence “it groweth upon the bare scalps of men and women that have lyen long ... in former times much accounted of because it is rare and hardly gotten, but in our own times much more set by, to make the ‘Unguentum Sympatheticum’ which cureth wounds without the local application of salves ... but as Crollius hath it, it should be taken from the sculls of those that have been hanged or executed for offences.” Ray[1270] says that the same gruesome plant “is celebrated by several authors as useful in haemorrhages and is said to be an ingredient of the famous ‘Unguentum Armarium[1271],’ reported to have been invented by Paracelsus.” Another lost ointment!

_c._ CURE FOR HYDROPHOBIA. Still another lichen to which extraordinary virtue was ascribed, was the very common ground species _Peltigera canina_ (Fig. 54), a preparation of which was used in the cure of rabies. Dillenius[1272] has published in full the prescription as “A certain Cure for the Bite of a Mad Dog” which was given to him by a very celebrated physician of that day, Dr Richard Mead, who had found it effective:

“Let the patient be blooded at the arm, nine or ten ounces. Take of the herb called in Latin _Lichen cinereus terrestris_, in English Ash-coloured ground liverwort, clean’d, dry’d and powder’d half an ounce. Of black pepper powder’d two drachms.

“Mix these well together and divide the Powder into four Doses, one of which must be taken every Morning, fasting, for four Mornings successively in half a Pint of Cow’s Milk warm. After these four Doses are taken, the Patient must go into the cold bath, or a cold Spring or River, every Morning fasting, for a Month. He must be dipt all over but not stay in (with his head above water) longer than half a minute, if the Water be very cold. After this he must go in three Times a Week for a Fortnight longer.”

Lightfoot[1273], some forty years later, refers to this medicine as “the once celebrated ‘Pulvis antilyssus,’ much recommended by the great Dr Mead.” He adds that “it is much to be lamented that the success of this medicine has not always answered the expectation. There are instances where the application has not prevented the Hydrophobia, and it is very uncertain whether it has been at all instrumental in keeping off that disorder.” Belief in the efficacy of the powder died out before the end of the century but the echo of the famous remedy remains in the name _Peltigera canina_, the dog lichen.

_d._ POPULAR REMEDIES. Lichens with very few exceptions are non-poisonous plants. They owed their repute as curative herbs to the presence in the thallus of lichenin and of some bitter or astringent substances, which, in various ailments, proved of real service to the patient, though they have now been discarded in favour of more effective drugs. Some of them, on account of their bitter taste, were frequently used as tonics to replace quinine in attacks of fever. Several species of _Pertusaria_, such as the bitter _P. amara_ (Fig. 132), and of _Cladonia_ as well as _Cetraria islandica_ (Fig. 128), were recommended in cases of intermittent fever; species of _Usnea_ and others, as for instance _Evernia furfuracea_, were used as astringents in haemorrhages; others were given for coughs, _Cladonia pyxidata_ (Fig. 69) being supposed to be specially valuable in whooping cough.

One of the most frequently prescribed lichens was the tree lung-wort (Lobaria pulmonaria) (Fig. 72). It was first included among medical plants by Dorstenius[1274], a Professor at Marburg; he gives a good figure and supplies directions for its preparation as a cure for chest complaints. The doctrine of “signatures” influenced practitioners in its favour, but it contains lichenin which acts as an emollient. In England, it was taken up by the famous Dr Culpepper[1275], who, however, believed in astrology even more than in signatures. He says: “it is of great use with many physicians to help the diseases of the lungs and for coughs, wheesings and shortness of breath which it cureth both in man and beast.” He adds that “Jupiter seems to own the herb.” A century later we find Dr John Hill[1276], who was a physician as well as a naturalist, stating that the great tree lung-wort has been at all times famous in diseases of the breast and lungs, but by that time “it was not much used owing to change in fashions.”

The only lichen that has stood the test of time and experience as a real remedy is _Cetraria islandica_, and even the “Iceland moss” is now rarely prescribed. The first mention in literature of this famous plant occurs in Cordus[1277] as the _Muscus_ with crisp leaves. Some years later it figures among the medicinal plants in Sibbald’s[1278] _Chronicle of the Scottish Flora_, and Ray[1279] wrote of it about the same time as being known for its curative and alimentary properties. It was Linnaeus[1280], and later Scopoli[1281], who gave it the important place it held so long in medicine. It has been used with advantage in many chronic affections as an emollient and tonic. Cramer[1282] in a lengthy dissertation gathered together the facts pertaining to its use as a food, a medicine and for dyeing, and he gives recipes he had himself prescribed with marked success in many different maladies. It has been said that if “Iceland moss” accomplished all the good it was alleged to do, it was indeed a “Divine gift to man.”

The physiological action of cetrarin (acid principle of the lichen) on living creatures has been studied by Kobert[1283] and his pupils. It has not any poisonous effect when injected into the blood, nor does it work any harm when taken into the stomach even of small animals, so that it may be safely given to the most delicate patients. Nearly always after small doses peristaltic movements in the intestines are induced which indicate that as a drug it might be of service in the case of enfeebled organs. In larger doses it may cause collapse in animals, but if administered as free cetraric acid it passes through the stomach unchanged to become slowly and completely dissolved in the intestine. The mucous membrane of the intestine of animals that had been treated with an overdose, was found to be richer in blood so that it seems as if cetrarin might be of service in chlorosis and in assisting digestion.

Cetrarin has also been proved to be a nerve excitant which might be used with advantage in mental maladies.

C. LICHENS AS POISONS

Though the acid substances of lichens are most of them extremely irritating when taken internally, very few lichens are poisonous. Keegan[1284] writing on this subject considers this quality of comparative innocuousness as a distinctive difference between fungi and lichens and he decides that it proves the latter to be higher organisms from a physiological point of view: “the colouring matters being true products of deassimilation, whereas those of fungi are decomposition or degradation waste products of the albuminoids akin to alkaloids.”

The two outstanding exceptions to this general statement are the two Alpine species _Letharia vulpina_ and _Cetraria pinastri_. The former contains vulpinic acid in the cortical cells, the crystals of which are lemon-yellow in the mass. _Cetraria pinastri_ produces pinastrinic acid in the hyphae of the medulla and the crystals are a beautiful orange or golden yellow.

These lichens, more especially _Letharia vulpina_, have been used by Northern peoples to poison wolves. Dead carcasses are stuffed with a mixture of lichen and powdered glass and exposed in the haunts of wolves in time of frost. Henneguy[1285], who insists on the non-poisonous character of all lichens, asserts that the broken glass is the fatal ingredient in the mixture, but Kobert[1286], who has proved the poisonous nature of vulpinic acid, says that the wounds caused by the glass render the internal organs extremely sensitive to the action of the lichen.

Kobert, Neubert[1287] and others have recorded the results of experiments on living animals with these poisons. They find that _Letharia vulpina_ either powdered or in solution has an exciting effect on the mucous membrane. Elementary organisms treated with a solution of the lichen succumbed more quickly than in a solution of the acid as a salt. Kobert concluded that vulpinic acid is a poison of protoplasm.

He further tested the effect of the poison on both cold- and warm-blooded animals. Administered as a sodium salt, 4 mg. proved fatal to frogs. The effect on warm-blooded animals was similar. A sodium salt, whether swallowed or administered as subcutaneous or intravenous injections, was poisonous. Cats were the most sensitive—hedgehogs the least—of all the animals that were subjected to the experiments. Volkard’s[1288] synthetic preparation of vulpinic acid gave the same results as the solution directly extracted from the lichens.

D. LICHENS USED IN TANNING, BREWING AND DISTILLING

The astringent property in _Cetraria islandica_ and in _Lobaria pulmonaria_ has been made use of in tanning leather. The latter lichen grows commonly on oak and could hardly be gathered in sufficient quantity to be of commercial importance. Like many other lichens it develops very slowly. _Lobaria pulmonaria_ has also been used to replace hops in the brewing of beer. Gmelin[1289] in his journey through Siberia visited a monastery at Ussolka where the monks employed it for this purpose. The beer tasted exactly like that made with hops, but was more intoxicating. The lichen in that country grew on pine-trees.

Lichens have in more modern times been used in the preparation of alcohol. The process of manufacture was discovered by Roy of Tonnerre, early in the nineteenth century, and was described by Léorier[1290]. It was further improved by Stenberg[1291], a Professor of Chemistry in Stockholm. Roy had worked with _Physcia ciliaris_, _Ramalina fraxinea_, _R. fastigiata_, _R. farinacea_ and _Usnea florida_, but Stenberg and distillers after his time[1292] made more use of _Cladonia rangiferina_ (Fig. 127), _Cetraria islandica_ (Fig. 128) and _Alectoria jubata_.

By treatment with weak sulphuric or nitric acid the lichenin of the thallus is transformed into glucose which on fermentation forms alcohol. Stenberg found that 68 per cent. of the weight in _Cladonia rangiferina_ was a “sugar” from which a good brandy could be prepared: a kilogramme of the lichens furnished half a litre of alcohol. The Professor followed up his researches by establishing a distillery near Stockholm. His papers contain full instructions as to collecting and preparing the plants. Henneguy[1293], writing in 1883, stated that the fabrication of alcohol from lichens was then a large and increasing industry in Sweden. The whole industry seems, however, to have fallen into disuse very soon: Wainio[1294], quoting Hellbom[1295], states that the various distilleries were already closed in 1884, because of the exhaustion of the lichen in the neighbourhood, and the impossibility of obtaining sufficient supplies of such slow-growing plants.

E. DYEING PROPERTIES OF LICHENS

_a._ LICHENS AS DYE-PLANTS. Knowledge as to the dyeing properties of lichens dates back to a remote antiquity. It has been generally accepted that lichen-colours are indicated by the prophet Ezekiel in his denunciation of Tyre: “blue and purple from the Isles of Elishah was that which covered thee.” Theophrastus describes certain plants as growing in Crete, and being used to dye wool, etc., and Pliny in his _Phycos Thalassion_ is also understood as referring to the lichen _Roccella_, “with crisp leaves, used in Crete for dyeing garments.”

Information as to the dyeing properties of certain lichens is given in most of the books or papers dealing with these plants from the herbals onwards. Hoffmann[1296] devoted a large part of his _Commentatio de vario Lichenum usu_ to the dye-lichens, and, illustrating his work, are a series of small rectangular coloured blocks representing samples of woollen cloth dyed with different lichens. There are seventy-seven of these samples with the colour names used by French dyers.

An important treatise on the subject translated into French was also contributed by Westring[1297]. He desired to draw attention to the tinctorial properties of lichens other than the _Roccellae_ which do not grow in Sweden. The Swedes, he states, already used four to six lichens as dye-plants, but only for one colour. He demonstrated by his improved methods that other colours and of finer tint could be obtained. He describes the best methods both of extraction and of dyeing, and then follows with an account of the different lichens likely to be of service. The treatise was subsequently published at greater length in Swedish[1298] with twenty-four very fine coloured illustrations of the lichens used, and with sample blocks of the colours to be obtained.

_b._ THE ORCHIL LICHEN, ROCCELLA. The value of _Roccella_ as a dye-plant had been lost sight of until it was accidentally rediscovered, early in the fourteenth century, by a Florentine merchant called Federigo. He introduced its use into Florence, and as he retained the industry in his own hands he made a large fortune, and founded the family of the Orcellarii, called later the Rucellarii or Rucellai, hence the botanical name, _Roccella_. The product was called _orseille_ for which the English name is orchil or archil. Another origin suggested for orchil is the Spanish name of the plant, _Orcigilia_. There are a number of different species that vary in the amount of dye-product. Most of them grow on rocks by the sea-side in crowded bluish-grey or whitish tufts of strap-shaped or rounded stiff narrow fronds varying in length up to about six inches or more. The main supply of “weeds” came from the Levant until the fifteenth century when supplies were obtained from the Canaries (long considered to produce the best varieties), Cape Verd and the African coasts. The geographical distribution of the _Roccellae_ is very wide: they grow on warm sea-coasts all over the globe, more particularly in Angola, the Cape, Mozambique, Madagascar, in Asia, in Australia, and in Chili and Peru.

Zopf[1299] has proved the existence of two different colouring substances among the Roccellas: in _R. fuciformis_ (Fig. 57) and _R. fucoides_ (both British species), in _R. Montagnei_ and _R. peruensis_ the acid present is erythrin; in _R. tinctoria_, _R. portentosa_ and _R. sinuensis_ it is lecanoric acid. In _R. tinctoria_ (Fig. 133), according to Ronceray[1300], the acid is located chiefly in the gonidial layer and the soredia but is absent from the cortex and centre. In _R. portentosa_ it is abundant in the cortex and central layer, while scarcely to be detected in the gonidial layer, and it is wanting altogether in the soredia. In _R. Montagnei_ it is chiefly found in the cortex and the gonidial layer, and is absent from the soredia and from the medulla.

_c._ PURPLE DYES: ORCHIL, CUDBEAR AND LITMUS. Orseille or orchil is formed not only from erythrin and lecanoric acid (orseillic acid), but also from erythrinic, gyrophoric, evernic and ramalic acids[1301] and may be obtained from any lichen containing these substances. By the action of ammonia the acids are split up into orcin and carbonic acid. In time, under the influence of ammonia and the oxygen of the air[1302], orcin becomes orcein which is the colouring principle of orchil; the perfecting of the process may take a month. The dye is used for animal fibres such as wool and silk; it has no effect on cotton.

There are several different preparations on the market, chiefly obtained from France and Holland; orchil or orseille in the form of a solution, cudbear (persio of Germany) almost the same, but manufactured into a violet-reddish powder, and litmus (tournesol of France) which is prepared in a slightly different manner. At one time the lichen, broken into small pieces, was soaked in urine; a fermentation process was set up, then lime and potash with an admixture of alum were added. The mass of material when ready was pressed into cubes and dried in the air. Commercial litmus contains three substances, erythrolein, erythrolitmin and azolitmin; the last named, which is the true litmus, is a dark brown amorphous powder soluble in water, and forming a blue solution with alkalies.

An aqueous solution of litmus when exactly neutralized by an acid is violet coloured; it becomes red with the smallest trace of free acid, or blue with free alkali. Litmus paper is prepared by steeping specially prepared unsized paper in the dye solution. It is as a ready and sensitive indicator of acidity or alkalinity that litmus is of so much value. According to Zopf[1303] it is also used as a blueing agent in washing and as a colouring of wine. Litmus is chiefly manufactured in Holland. Still another substance somewhat differently prepared from the same lichens is sold as French purple, a more brilliant and durable colour than orchil.

_d._ OTHER ORCHIL LICHENS. Though species of _Roccella_ rank first in importance as dye-plants, purple and blue colours are obtained, as indicated above, from other very different lichens. Lindsay[1304] extracted orchil from about twenty species. Those most in use in northern countries are on the whole less rich in colouring substances; they are: _Umbilicaria pustulata_, species of _Gyrophora_, _Parmelia_ and _Pertusaria_, and above all _Lecanora tartarea_ (Fig. 134). The last named, one of the hardiest and most abundant of rock- or soil-lichens, is chiefly used in Scotland and Sweden (hence the name “Swedish moss”) to furnish a red or crimson dye. In Scotland all dye-lichens are called “crottles,” but the term “cudbear” was given to _Lecanora tartarea_ (either the lichen or the dye-product); it was acquired from a corrupt pronunciation of the Christian name of Dr Cuthbert Gordon, a chemist, who, according to Bohler[1305], obtained a patent for his process of producing the dye, or who first employed it on a great scale in Glasgow. Johnson[1306] remarks that the colour yielded by cudbear, if well prepared, is a fine, clear, but not very bright purple. It is, he alleges, not permanent. Like other orchil substances it is without effect on cotton or linen.

_e._ PREPARATION OF ORCHIL. A general mode of treatment of dye-lichens recommended by Lauder Lindsay[1307] for home production of orchil, cudbear and litmus is as follows:

1. Careful washing, drying and cleansing to separate earthy and
other impurities.

2. Pulverization into a coarse or fine pulp with water.

3. Repeated addition of ammoniacal liquor of a certain strength,
obtainable from several sources (_e.g._ putrid urine, gas liquor,
etc.).

4. Frequent stirring of the fermenting mass so as to ensure full
exposure of every part thereof to the action of atmospheric
oxygen.

5. Addition of alkalies in some cases (_e.g._ potash or soda),
to heighten or modify colour; and of chalk, gypsum and other
substances to impart consistence.

_f._ BROWN AND YELLOW DYES. The extracting of these colours from lichens is also a very old industry. Linnaeus found during his journey to Lappland[1308], undertaken when he was quite a young man, that the women in the northern countries made use of a brown lichen for dyeing which is evidently _Parmelia omphalodes_ (Fig. 135). He describes it as a “rich _Lichenoides_ of a brown stercoraceous colour,” and he has stated that it grew in such abundance in the Island of Aland, that every stone was covered, especially near the sea. In the _Plantae tinctoriae_[1309] there is a record of six other lichens used for dyeing: _Lichen Roccella_, _L. tartareus_, _L. saxatilis_, _L. juniperinus_, _L. parietinus_ and _L. candelarius_. The value of _Lichen omphalodes_ was also emphasized by Lightfoot; the women of Scotland evidently appreciated its dyeing properties as much as other northern peoples.

A series of memoirs on the utility of lichens written by Willemet[1310], Amoreux and Hoffmann, and jointly published at Lyons towards the end of the eighteenth century, represents the views as to the economic value of lichens held by scientific botanists of that time. All of them cite the various dye-species, and Hoffmann, as already stated, gives illustrations of colours that can be obtained. It has been once and again affirmed that _Parmelia saxatilis_ yields a red colour, but Zopf[1311] denies this. It contains saxatillic acid which is colourless when extracted but on boiling gives a clear reddish-yellow to reddish-brown solution which dyes wool and silk directly without the aid of a mordant. Zopf[1311] observed the process of dyeing followed in South Tyrol: a layer of the lichen was placed in a cooking pot, above this a layer of the material to be dyed, then lichen and again the material until the pot was filled. It was covered with water and boiled three to four hours, resulting in a beautiful rust-brown and peculiarly fast dye.

Reddish- or rust-brown dye is also obtained from _Haematomma ventosum_ and _H. coccineum_, a yellow-brown from _Parmelia conspersa_ (salazinic acid), and other shades of brown from _Parmelia perlata_, _P. physodes_, _Lobaria pulmonaria_ and _Cetraria islandica_.

Yellow lichens in general furnish yellow dyes, as for instance _Xanthoria parietina_ which gives either brown or yellow according to treatment and _Cetraria juniperina_ which forms a beautiful yellow colouring substance on boiling. _Teloschistes flavicans_ and _Letharia vulpina_ yield very similar yellow dyes, and from _Lecanora parella_ (Fig. 39), _Pertusaria melaleuca_ and _Usnea barbata_ yellow colours have been obtained. _Candelariella vitellina_ and _Xanthoria lychnea_ both contain yellow colouring agents and have been employed by the Swedes for dyeing the candles used in religious ceremonies.

_g._ COLLECTING OF DYE-LICHENS. Lauder Lindsay[1312] made exhaustive studies of dye-lichens both in the field and in the laboratory, and recorded results he obtained from the micro-chemical examination of 540 different specimens. He sought to revive and encourage the use of their beautiful colour products among country people; he has given the following practical hints to collectors:

1. That crustaceous dwarf pale-coloured species growing on rocks, and especially on sea-coasts, are most likely to yield red and purple dyes similar to orchil, cudbear or litmus; while on the other hand the largest, most handsome foliaceous or fruticose species are least likely.

2. That the colour of the thallus is no indication of colorific power (in orchil lichens), inasmuch as the red or purple colouring substances are the result of chemical action on crystalline colorific “principles” previously devoid of colour.

3. That alterations in physical characters, chemical composition and consequently in dyeing properties are very liable to be produced by modification in the following external circumstances:

(i) Degree of moisture.
(ii) Degree of heat.
(iii) Degree of exposure to light and air.
(iv) Climate.
(v) Elevation above the sea.
(vi) Habitat; nature of basis of support.
(vii) Age.
(viii) Seasons and atmospheric vicissitudes, etc.

August has been recommended as the best month for collecting dye-lichens: _i.e._ just after the season of greatest light and heat when the accumulation of acids will be at its maximum.

Some of the acids found useful in dyeing occur in the thalli of a large number of lichens, many of which are too scantily developed to be of any economic value. Thus salazinic acid which gives the effective yellow-brown dye in _Parmelia conspersa_ was found by Zopf in 13 species and varieties. It has since been located by Lettau[1313] in 72 different lichens, many of them, however, with poorly developed or scanty thalli, so that no technical use can be made of them.

_h._ LICHEN COLOURS AND SPECTRUM CHARACTERS. In a comparative study of vegetable colouring substances, Sorby[1314] extracted yellow colouring matters from various plants distinguished by certain spectrum characters. He called them the “lichenoxanthine group” because, as he explains, “these xanthines occur in a more marked manner in lichens than in plants having true leaves and fronds.” Orange lichenoxanthine he found in _Peltigera canina_, _Platysma glaucum_, etc., when growing well exposed to the sun. Lichenoxanthine he obtained from the fungus _Clavaria fusiformis_; it was difficult to separate from orange lichenoxanthine. Yet another, which he terms yellow lichenoxanthine, he obtained most readily from _Physcia_ (_Xanthoria_) _parietina_. The solutions of these substances vary according to Sorby in giving a slightly different kind of spectrum. He did not experiment on their dyeing properties.

F. LICHENS IN PERFUMERY

_a._ LICHENS AS PERFUMES. There are a few lichens that find a place in Gerard’s[1315] _Herball_ and that are praised by him as being serviceable to man. Among others he writes of a “Moss that partakes of the bark of which it is engendered. It is to be used in compositions which serve for sweet perfumes and that take away wearisomeness.” At a much later date we find Amoreux[1316] recording the fact that _Lichen_ (_Evernia_) _prunastri_, known as “Mousse de Chêne,” was used as a perfume plant.

Though lichens are not parasitic, the idea that they owed something of their quality to the substratum was firmly held by the old herbalists. It appears again and again in the descriptions of medicinal lichens, and still persists in this matter of perfumes. Hue[1317] states in some notes to a larger work, that French perfumers extract an excellent perfume from _Evernia prunastri_ (Fig. 59) known as “Mousse des Chênes” (Oak moss), and it appears that the plants which grow on oak contain more perfume than those which live on other trees. The collectors often gather along with _Evernia prunastri_ other species such as _Ramalina calicaris_ and _R. fraxinea_, but these possess little if any scent. A still finer perfume is extracted[1318] from _Lobaria pulmonaria_ called “moss from the base of the oaks,” but as it is a rarer lichen than _Evernia_ it is less used. Most of the Stictaceae, to which family _Lobaria_ belongs, have a somewhat disagreeable odour, but this one forms a remarkable exception, which can be tested by macerating the thallus and soaking it in spirit: it will then be found to exhale a pleasant and very persistent scent. These lichens are not, however, used alone; they are combined with other substances in the composition of much appreciated perfumes. The thallus possesses also the power of retaining scent and, for this reason, lichens frequently form an ingredient of potpourri.

_b._ LICHENS AS HAIR-POWDER. In the days of white-powdered hair, use was occasionally made of _Ramalina calicaris_ which was ground down and substituted for the starch that was more commonly employed.

In older books on lichenology constant reference is made to a hair-powder called “Pulvis Cyprius” or “Cyprus powder” and very celebrated in the seventeenth century. It was believed to beautify and cleanse the hair by removing scurf, etc. _Evernia prunastri_ was one of the chief ingredients of the powder, but it might be replaced by _Physcia ciliaris_ or by _Usnea_. The virtue of the lichens lay in their capacity to absorb and retain perfume. The powder was for long manufactured at Montpellier and was a valuable monopoly. Its composition was kept secret, but Bauhin[1319] (J.) published an account of the ingredients and how to mix them. Under the title “Pulvis Cyprius Pretiosius” a more detailed recipe of the famous powder was given by Zwelser[1320], a Palatine medical doctor. The lichen employed in his preparation, as in Bauhin’s, is _Usnea_, but that may include both _Evernia_ and _Physcia_ as they are all tree plants. He gives elaborate directions as to the cleaning of the lichen from all impurities—it is to be beaten with a stick, washed repeatedly with limpid and pure water, placed in a linen cloth and dried in the sun till it is completely bleached and deprived of all odour and taste.

When well dried it was placed in a basket in alternate layers with freshly gathered, entire flowers of roses and jasmine (or flowers of orange and citrus when possible). The whole was compressed by a heavy weight, and each day the flowers were renewed until the “Usnea” was thoroughly impregnated with a very fragrant odour. It was then reduced to a fine powder and ready for other ingredients. To each pound should be added:

1-1/2 oz. powdered root of white Iris.

1-1/2 oz. of _Cyperus_ (a sedge).

1 scruple or half drachm of musk reduced to a pulp with fragrant spirit of roses.

1/2 drachm of ambergris dissolved in a scruple of genuine oil of roses, or oil of jasmine or oranges as may be preferred.

Zwelser adds:

“This most fragrant royal powder when sprinkled on the head invigorates by its remarkably pleasant odour; by its astringency and dryness it removes all impurities, and, since it operates with no viscosity nor sticks firmly either to skin or hair, it is easily removed from the hair of the head.”

G. SOME MINOR USES OF LICHENS

The possibility of extracting gum or mucilage from lichens was demonstrated by the Russian scientist, Professor Georgi[1321], and later by Amoreux[1322], the method employed being successive boiling of the plants. The larger foliose or fruticose forms were specially recommended.

At a later date, during the Napoleonic wars, the “ingenious Lord Dundonald[1323],” of great fame as an inventor, published an account of the extraction process and of the application of the gum to calico-printing, staining and manufacture of paper, dressing and stiffening silks. Lord Dundonald’s aim was to replace the gum Senegal, then a monopoly of the French, who were in possession of the Settlement of Senegambia. He took out a patent for his invention, but whether the gum was successfully used is not recorded.

According to Henneguy[1324], lichen mucilage, as a substitute for gum arabic, has been used at Lyons with advantage in the fabrication of dyed materials.