Lichens

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:

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.

APPENDIX
POSTSCRIPT TO CHAPTER VII[1325]

In a remarkable paper on The Symbiosis of Lichens[1326], Dr A. Henry Church has presented a new and striking view of the origin and development of lichens: he has sought to link them up with other classes of vegetation that, in the great transmigration, passed from sea to land. As we know from his Thalassiophyta[1327] and the subaerial transmigration, he holds that primeval algae of advanced form and structure were left exposed on dry land by the gradually receding waters, and those that successfully adapted themselves to the changed conditions formed the basis of the land flora. A certain number of the algae lost their surface tissues containing chlorophyll and they had perforce to secure from other organic sources the necessary carbohydrates: they adopted a heterotrophic existence as saprophytic or parasitic fungi. Fungi are a backward race (deteriorated according to Dr Church) as regards their soma, but in number, distribution and variety of spore-production, they are eminently successful plants.

Lichens are similarly regarded by Dr Church as derived from stranded contemporaneous types of marine algae—crustaceous, foliose and fruticose, that had also lost their chlorophyll, but by taking into association green algal units of a lower grade they established a vicarious photosynthesis. But, to quote his own words[1328], “as the alga-lichen-fungus left the sea, so it remained: it might deteriorate, but it certainly never advanced, once the sea factors which produced it were eliminated, it simply stopped along these lines.”

And again[1329]: “Lichens thus present an interesting case of an algal race deteriorating along the lines of a heterotrophic existence, yet arrested, as it were, on the somatic down-grade, by the adoption of intrusive algal units of lower degree to subserve photosynthesis (much in the manner of the marine worm Convoluta). Thus arrested, they have been enabled to retain more definite expression of more deeply inherent factors of sea-weed habit and construction than any other race of fungi; though closely paralleled by such types as Xylaria (Ascomycete) and Clavaria (Basidiomycete), which have followed the full fungus progression as holosaprophytic on decaying plant residues.”

Dr Church’s theory is of vivid interest and might be convincing were there no possibility and no proof of advance within the symbiotic plant, but in numbers of crustaceous thalli, there is evident, by normal or abnormal[1330] development, the first advance to the formation of rudimentary squamules, a condition diagnosed as subsquamulose. “Deterioration” of the lichen plant—when it occurs owing to unfavourable conditions—is a reversion to the leprose early stage of the association; there is no evidence of reversion from fruticose or foliose to squamulose. A glance at the table of lichen phyla[1331] shows progression again and again from the crustaceous forms onwards. In such a phylum as Physciaceae (with colourless polarilocular spores) there is a clear example of a closely connected series; the different types of thallus—crustaceous, squamulose, foliose and fruticose—are all represented and form a natural sequence, being well delimited by the unusual form of the spore and by the presence of parietin in thallus or apothecium.

That there has been development seems absolutely certain, and that along the lines sketched in the chapter on phylogeny. Progress has been mainly in the thallus, but there has also been change and advance in the reproductive organs, more especially in the spores which in several families reach a size and septation unparalleled in fungi. That association with green algal cells stimulated the fungus to new development is the view taken of the lichen plant and emphasized in the present volume. But it seems more in accordance with the polyphyletic origin and recurring parallel development in the phyla that association began at the elementary crustaceous stage, and that the lichen soma was gradually evolved within what is after all a very limited and simple structure.

ADDENDUM
Footnote to Page 404

E. M. Holmes[1332] has published recently an account of a substance which seems in some respects to answer to the description of manna (Exodus xvi.; Numbers xi.) more nearly than the generally accepted Lecanora esculenta. The information is quoted from Swann’s book: Fighting the slave-hunters in Central Africa. The author writes (p. 116): “I was shown a curious white substance similar to porridge. It was found early in the morning before the sun rose. On examination it was found to possess all the characteristics of the manna ... of the Israelites. In appearance it resembled coriander seed, was white in colour like hoar frost, sweet to the taste, melted in the sun and if kept over night was full of worms in the morning. It required to be baked if you intended to keep it for any length of time. It looked as if it was deposited on the ground in the night.” The writer has suggested that “the substance might be mushroom spawn as, on the spot where it melted tiny fungi sprung up the next night.” Swann’s statement has been confirmed by Dr Wareham, a medical missionary from the same district, who states, however, that it is of rare occurrence.