A Popular History of British Lichens.
Genus II. Roccella.

A Popular History of British Lichens, comprising an account of their structure, reproduction, uses, distribution and classification. By W. Lauder Lindsay, M.D., Fellow of the Botanical and Royal Physical Societies of Edinburgh, etc. Lovell Reeve, 5, Henrietta Street, Covent Garden. Lontoo 1856.

(Tekstiin lisätty kappaleita lukemisen helpottamiseksi. // Some paragraphs added to the original text for making reading easier.)


Gen. Char. Thallus fruticulose, segments springing from a common base, round or thong-like, equal or nodulose, erect or pendulous, glaucous, everywhere of similar colour, having a cartilaginous cortical layer: very frequently sorediiferous. Apothecium scutellate, its exciple being innate in the thallus, normally lateral. Thalamium at first covered by a thalline veil, afterwards naked, black.

Generic term derived from the Portuguese word rocha, a rock, in allusion to the habitat of most of the species; or from the name of the family of the Florentine merchant (Oricellarii, or Rucellai) who was the first to manufacture from them the now familiar dye Orchill.

1. Roccella tinctoria (tinctura, a colour or dye). Thallus round, at length nodulose or warted; segments simple or bifurcate, naked or sorediiferous; old thallus frequently becomes much elongated, pendulous or trailing, rarely branched; apothecia lateral. (E. B. 211.)

Its spermogones are frequently absent; when present they are readily recognized as black points scattered over the whitish thallus. They are globular, unilocular, and im mersed; their spermatia are linear and feebly curved. There is considerable variety in the form of the apothecia. Some times they are regularly patellate, resembling the apothecia of Lecidea; at other times they are misshapen tubercles, appearing to have burst through the cortical layer, which forms around them an irregular thalline exciple; the latter state is the more usual, but is probably an abnormal con dition of the former. The spores of both are alike, being ellipsoid-oblong, straight or slightly curved, generally quadrilocular or triseptate, nearly colourless or pale yellow, re sembling somewhat those of Peltigera and Sticta.

Its habitat is maritime rocks; it grows to a very limited extent on the Isle of Portland, Guernsey, and other points on or near the south coast of England. It is more abundant on the Mediterranean shores, but reaches its maximum development only in tropical or warm climates, where however it has a somewhat wide geographical range.

2. Roccella fuciformis (fucus, a species of seaweed). Thallus flattened or thong-like, irregularly divided, often fan-shaped; segments variously bent, naked or sorediiferous; apothecia lateral and superficial.

It grows, like the preceding species, chiefly on maritime rocks; but in some foreign countries it is found also on trees, as at Pondicherry, in India, where its habitat is the trunk of the Mangifera Indica. It occurs very sparingly on the south coast of England, in the Channel Islands, and on the adjacent islands and coasts of France. But it is only in tropical Africa, Asia, and South America, that it reaches its highest development; on the coasts of these countries it frequently attains great size, and has a very tough leathery consistence.

It usually has a greater abundance of apothecia, and is more seldom warted or mealy, but more frequently cracked and fissured, than R. tinctoria. Its colour is generally tawny or ochroleucous, and it varies much in the size and mode of division of its lacinise. Its geographical range is greater than that of the preceding species.

R. tinctoria and R. fuciformis may be considered types of the most valuable dye-species of the genus Roccella which we possess,—the "Orchella weeds" of commerce, which are divisible botanically into three classes:—1. Such as have a cylindrical tapering thallus; 2. those having a flattened or compressed thallus; and 3. a mixture of the two preceding forms.

Of the first class the chief varieties are "Canary," "Barbary, or Mogador," "thick Lima," and "Cape" Or chella weeds; while of the second the principal are the "Angola," "Madagascar," and "thin Lima" weeds. Of these the most valuable kind at present is the Angola weed, from the Portuguese settlement of Angola, in South Africa; it is about an inch and a half to two inches in length.

The Canary variety, which includes the "Cape de Verde weed" from the Canary, Cape de Verde, and adjacent islands off the west coast of Northern Africa, has been the longest known in commerce; it is a delicate filiform species about half an inch to an inch and a half long, and frequently of a dark brownish colour. Next to these the Lima varieties, from the west coast of South America, are greatly used by the orchill-maker. The thick form is frequently six to eight inches long, with thick tough segments, sometimes superior in diameter to a goose-quill; it usually occurs in the form of fragments having a reddish cross section.

The thin variety has the characters described under R.fuciformis. The Cape, Barbary or Mogador, and Madagascar forms are inferior in size and quality.

*Vide Paper by the Author in the 'Edinburgh New Philosophical Journal,' July, 1855, on the "Dyeing Properties of Lichens."Besides R. tinctoria and R. fuciformis, and the varieties hypomecha of the former and linearis of the latter, the chief botanical sources of these Orchella weeds are R. Montagnei, R. pygmæa, R. flaccida, R. phycopsis, and R. dichotoma. Comparatively numerous as are their geographical sources, many new and probably superior fields of export remain to be opened up to British commercial enterprise; in illustration of which we need only cite the vast fields of India and the Indian Archipelago, the shores of Africa and Asia bordering on the Bed Sea, New Zealand, New South Wales, and many of the Pacific Islands. The Boccellas grow abundantly on the arid rocks of Aden, in Arabia; and the Indian and Ceylon specimens which we have seen are remarkable for their great size.*

The production of an export trade in dye-lichens might not only prove a boon to the poor inhabitants of many a hitherto barren-shore, but would probably become remunerative to British manufacturers who are at present paying high prices for the Angola weed and similar fine varieties of Orchella-weed, which are fast becoming scarce in the market.

Plants growing in arid situations in tropical countries are found richest in colorific principles; hence, as compared with species from tropical Africa, Asia, or South America, European species are worthless in commerce. Burnett illustrates this, by stating £290 per ton as the value of Canary Orchella-weed, while the same plant from Madeira will only bring £140, and from Barbary from £30 to £45, in the market. This is an instructive lesson on the influence of climate in the production of changes in the chemical composition or products of Lichens.

The estimated annual value of the imports of Orchella-weeds and other dye-lichens many years ago was stated at £60,000 to £80,000. Their value has been gradually rising in the English market. Half a century ago only inferior kinds were procured at prices ranging from £20 to £200 per ton; now very fine qualities are imported from various localities, probably at an average price of £200 to £400; and they have been known to rise so high as £1000 per ton.

While Italy enjoyed a monopoly in the manufacture of Orchill, large quantities were supplied by Teneriffe, the Canaries, Azores, and neighbouring islands; the inhabitants farmed out the right to gather the Orchella-weeds, paying therefor considerable sums to the Government. Prior to this the Orchella-weeds were known only in the islands and shores of the Levant; and their capability of yielding, by maceration in ammonia, a purple dye, was accidentally discovered by a Florentine merchant travelling there, who noticed that putrid urine tinged the plants red or purple. Returning home, he founded on the hint thus obtained the manufacture of Orchill, which he long carried on with great secrecy under the name of "Tournesol," and by which he realized a handsome fortune.

R. tinctoria possesses emollient or demulcent properties, and hence has been used to allay the tickling cough of phthisis and in other chest affections; these qualities depend on the presence of a certain amount of starchy and gummy matters. It contains, moreover, according to Nees von Esenbeck, resin, wax, and glutinous matter, tartrate and oxalate of lime, and chloride of sodium, the latter probably due to adherent sea-water. Its ash contains lime, soda, magnesia, alumina, silica, and peroxide of iron, in combination with carbonic, sulphuric, and phosphoric acids.

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