History.—Theophrastus [Hist. Plant. lib. iv. cap. vii. p. 82, ed. Heinsii, 1613.], Dioscorides [Lib. iv. cap. c. p. 283, ed. Saraceni, 1598.], and Pliny [Lib. xxvi. cap. lxvi.; and lib. xxxii. cap. xxii. ed. Valpy.], notice a plant which they respectively call ποντιον φυκος, φυκος θαλασσιον, and phycos thallassion, i. e., fucus marinus. They state that it grew near the ground on the rocks of Crete, and was used for dyeing purple; and Dioscorides says that some persons imagine that the paint (fucus) used by women was this plant, but, he adds, it was a root bearing the same name [Endlicher (Enchiridion Botanicum, p. 4, 1841) says, that one of the Algae, viz., Rytiphloea tinctoria, Ag. yields a red colour, the fucus of the ancients.].
The phycos thallassion has been usually assumed to be Roccella tinctoria, and not, as the ancients state, a sea-weed [Beckmann, Hist. of Invent. and Discov. translated by Wm. Johnston, vol. i. p. 59, 1797.]. Bory de St. Vincent [Essais sur les Isles Fortunées, 1803; Dict. Classiq. d'Hist. Nat. xiv. 1828.] even thinks that the ancients made their celebrated purple dye, brought from the isles of Elishah [Ezekiel, ch. xxvii. v. 7.], with the R. tinctoria, which he therefore calls R. purpura-antiquorum.
Early in the 14th century, the art of dyeing wool with Roccella tinctoria was made known at Florence by one of the descendants of a German nobleman named Ferro or Fredrigo. It is said that he accidentally discovered, in the Levant, the colour obtained by the action of urine on this plant, there called respio or respo, and in Spain orciglia; and that his family received the name of Oricellarii, altered to Rucellai, from this useful invention. From the latter term the generic name Roccella is supposed to be derived [Beckmann, op.citato.].
Botany. Gen. Char.—Thallus coriaceo-cartilaginous, rounded or plane, branched or laciniated. Apothecia orbicular, adnate with the thallus; the disk coloured, plano-convex, with a border at length thickened and elevated, formed of the thallus, and covering a sublentiform, black, compact, pulverulent powder concealed within the substance of the thallus (Hooker).
Sp. Char.—Thallus suffruticose, rounded, branched, somewhat erect, grayish-brown, bearing powdery warts [soredia]. Apothecia flat, almost black and pruinose, with a scarcely prominent border (Hooker).
β. R. tinctoria β hypomecha, Ach.; R. hypomecha, Bory. Thallus terete, filiform, very long, simplish, subconjugate, prostrate, pendulous.—Cape of Good Hope; Mauritius.—2 to 5 inches long: the thallus geniculate where the apothecia are developed (Bory): the apothecia by age lose the thalloid margin and become convex, naked, smooth, and black (Ach.).
γ. R. dichotoma, Ach., has a terete ash-gray, brownish thallus, with longish dichotomous branches.
Hab.—Maritime rocks of the eastern Atlantic islands (the Madeira isles, the Azores, the Canaries, and the Cape de Verd isles); western coast of South America (on porphyry near Riobamba in Colombia, and on the sea-shore near Chancay in Peru—Humboldt) [Synops. Plant. Aequin. i. 50.]; Bourbon; extreme south of England, Guernsey, Portland Island, and the Scilly Islands.
In commerce several other species, or varieties of the above species, are met with. The most important are the following:
R. fuciformis, De Cand., Ach. Syn. p. 244. Hooker, Engl. Fl. vol. v. part 1, p. 222. Lichen fuciformis, Linn. Flat leaved orchella weed.—Thallus flat, branched, nearly upright, grayish white, bearing powdery warts. Apothecia pruinose, bordered (Hooker). Maritime rocks with R. tinctoria; Canaries; from Cherbourg to Mogadore; St. Malo; South of England.
R.fuciformis β linearis, Ach. Spain, Sumatra, the Dezertas (Madeira).
R. phycopsis, Ach., is also perhaps a variety of R. fuciformis. It is intermediate in character between the latter and R. tinctoria. Its thallus is somewhat flattened (terete-compressed), and much branched; the divisions being somewhat fastigiate, rarely more than an inch long, and very farinaceous.
R. flaccida, Bory. Branches somewhat cylindrical, filiform, very broad, pendulous, whitish. Mauritius.
R. Montagnei, Belanger, Voy. aux Indes Orient. Pl. 13, Fig. 4 [no date]. Thallus coriaceous, flaccid, flat, entire and broad at the base, at length dichotomously (rarely trichotomously) laciniate, pale glaucous, sorediferous. Apothecia marginal, somewhat pedicellate, with a black convex pruinose disk, and persistent margin.—On the trunks of Mango trees (Mangifera indica) in India; especially at Pondicherry. This species, and R. pygmaea, D. R. and Mont, which grows in Algeria, are remarkable for growing on the trunks of trees; the others are found on maritime rocks.
Commerce.—All the species and varieties of Roccella found in commerce bear the general appellation of Orchella weed; but they are distinguished by the name of the country from which they are imported. The following is a list of the which, within the last few years, have been found in the London market; those marked with the asterisk (*) I have myself examined, and possess samples of—
* Angola Orchella weed.
Mauritius Orchella weed.
* Madagascar Orchella weed.
* Barbary (Mogdore) Orchella weed.
* Cape of Good Hope Orchella weed.
* Canary Orchella weed.
Cape de Verde Orchella weed.
* Western Island Orchella weed.
* Madeira (Dezertas) Orchella weed.
* Lima (thick) Orchella weed.
* Lima (thin) Orchella weed.
Corsica and Sardinia Orchella weed.
In 1838, 567 cwts.; in 1839, 6494 cwts.; and in 1840, 4175 cwts. of Orchella paid duty.
Physical Properties.—Having fully described the botanical characters of the different species of Roccella, it will be unnecessary here to describe minutely the different commercial sorts [For figures of the microscopic structure of the Roccella tinctoria, the reader is referred to Link's Icones Selectae Anatomico-Botanicae, Berl. 1841, 3tes Heft, Taf. vi.].
The commercial kinds of Orchella weed may be conveniently arranged in three divisions, as follows:—
1. Orchella weeds having a cylindrical tapering thallus.—These consist usually of Roccella tinctoria, and perhaps R. flaccida, Bory. In one case (Cape of Good Hope orchella) the plant is R. hypomecha, a mere variety of R. tinctoria. Occasionally, flattened orchella weeds are found intermixed: these may be regarded as accidental.
α. Canary Orchella Weed. Roccella tinctoria.—Formerly the most esteemed sort of Orchella. Thallus filiform, seldom exceeding in thickness a pin, and in length an inch and a half. Colour from pale-yellowish gray to dark brown.
β. Western Island Orchella Weed; St. Michael's Orchella Weed. Roccella tinctoria.—Similar to the preceding; but less valuable as a dye-stuff.
γ. Barbary Orchella Weed; Mogadore Orchella Weed. Roccella tinctoria.—Somewhat smaller than the preceding sorts, and less valuable as a dye.
δ. Lima thick Orchella Weed; South American thick Orchella Weed. Roccella tinctoria? R. flaccida, Bory?—A very handsome lichen, brought from Lima and other parts of the west coast of South America. Distinguished from the other sorts by its large size; usually several, sometimes six or eight, inches long: its thickness from that of a crow-quill to that of a goose-quill. Thick tubercular excrescences are frequently found on it. It has a very leathery, sometimes a cartilaginous whitish appearance. Its quality as a dye is considered good, and superior to the preceding sorts.
ε. Cape of Good Hope Orchella Weed. R. tinctoria β hypomecha, Ach.—A large lichen, though rather smaller than the preceding. Remarkable for its white or gray-white appearance: many of the divisions of the thallus are geniculated. As a dye its quality is very bad.
2. Orchella Weeds have a flat (plane) or compressed thallus. These consist of R. fuciformis, and, perhaps, in some cases, of R. Montagnei.
ζ. Angola Orchella Weed. R. fuciformis [Dr. Scouler (in Dr. Stenhouse's paper on the Lichens in the Phil. Trans. for 1848, p. 72) has pronounced the Angola Orchella Weed to be R. Montagnei of Belanger. My own examination of it led me to believe that it was R. fuciformis. I therefore submitted samples of it to Sir W. Hooker and Mr. Bennett, of the British Museum, both of whom have declared it to be one of the numerous varieties of R. fuciformis.].—Thallus very flat, seldom exceeding an inch and a half or two inches in length: in breadth (except at the fork or division) rarely more than one-sixth of an inch. Colour greenish or yellowish-gray. As a dye-stuff it is the most valuable of all the Orchella weeds.
η. Madagascar Orchella Weed. R. fuciformis.—Smaller, but in other respects similar to the preceding sort. Somewhat less valuable than the Angola sort.
θ. Lima thin Orchella Weed. R. fuciformis?—Somewhat more rounded or less flat than the preceding, which it in other respects very much resembles.
3. Mixed Orchella Weeds, consisting of both flat and round Orchella Weeds.
ι. Madeira Orchella Weed. R. tinctoria and R. fuciformis β linearis, Ach. Gathered on the The Dezertas, near Madeira. The round and terete thalli resemble the Canary Orchella. The flattened thalli are thicker than those of the Angola sort.
Composition.—A qualitative analysis of Roccella tinctoria was made by Fr. Nees v. Esenbeck [Brande's Archiv. d. Apothekerverein, Bd. xvi. S. 135.], who found in it a brown resin (soluble in alcohol and ether, and becoming brownish red with ammonia), wax, glutinous matter, insoluble starch, yellow extractive, yellowish-brown gummy matter, lichen-starch, tartrate and oxalate of lime, and chloride of sodium from the adherent sea water.
The nature of the colorific principles of the Orchella weeds (Roccella) of commerce has been the subject of several analytical investigations; the most important of which are those of Heeren [Schweigger's Jahrb. d. Chem. Bd. lix. S. 313, 1830; Buchner's Repertorium, Bd. xxxviii. S. 21.], in 1830; of Kane [Phil. Trans. for 1840, p. 273.], in 1840; of Schunck [Ann. d. Chem. u. Pharm. Bd. xli. S. 157, 1842; and Memoirs of the Chemical Society of London, vol. iii. p. 144, 1846.], in 1841, and also in 1846; of Rochleder and Heldt [Ann. d. Chem. u. Pharm. Bd. xlviii. S. 1, 1843.], in 1843; of Knop [Ibid. Bd. xlix. S. 102, 1844.], in 1844; and of Stenhouse [Phil. Trans. for 1848, p. 63.], in 1848.
Robiquet [Journ. de Chim. Méd. t.v.p. 324, 1829; Journ. de Pharm. t. xxi. pp. 269 and 387, 1835.] has thrown much light on the subject by his investigations into the nature of the colorific principle of Variolaria dealbata. The only constituents of the Orchella weeds which will require separate notice are the colorific principles; and in describing these I shall follow Stenhouse.
1. Alpha-Orsellic Acid (Stenhouse); Colorific principle of Lima thick Orchella Weed (Roccella tinctoria).—Obtained by macerating the lichen in milk of lime, and then adding excess of hydrochloric acid to the filtered solution. A white gelatinous precipitate is obtained, which, when washed, dried, dissolved in warm alcohol, and the solution allowed to cool, yields stellate prismatic crystals of alpha-orsellic acid. It is nearly insoluble in cold water, but sparingly soluble in boiling water; pretty soluble in cold alcohol and ether, and readily so in boiling alcohol. It reddens litmus, and forms crystallizable salts with the alkalies and earths. Its most characteristic reaction, by which its presence can be very readily detected, is the deep blood-red colour which it instantly strikes with a solution of hypochlorite of lime; the colour soon changes to yellow which gradually also disappears. A solution of orsellic acid in ammonia, on exposure to the air, soon assumes a bright-red colour, which gradually becomes darker and purple coloured. The rational formula for alpha orsellic acid is C32H15O3+HO.
2. Beta-Orsellic Acid (Stenhouse); Colorific principle of Cape of Good Hope Orchella Weed (Roccella hypomecha).—Is intermediate in its properties between alpha-orsellic acid and erythric acid, but approaches the former more closely. It is crystallizable, and its solution yields a fugitive blood red colour with hypochlorite of lime. Its ammoniacal solution also becomes red in the air. The rational formula of the hydrated acid is C34H17O14+HO.
3. Erythric Acid (Schunck and Stenhouse); Colorific principle of Angola and Madagascar Orchella Weeds (Roccella fuciformis)—By macerating the lichen in milk of lime, as before stated, Stenhouse obtained 12 per cent. of crude erythric acid. It is a feebler acid than alpha- and beta-orsellic acids; but it agrees with these acids in being crystallizable, and in yielding red coloured compounds with ammonia, and also in its reaction with hypochlorite of lime. The formula of the hydrated acid is C20H10O9+HO.
Chemical Characteristics.—The aqueous decoction of Orchella weed forms a copious precipitate with diacetate of lead, and has its colour deepened by alkalies. Digested in a weak solution of ammonia, in a corked phial, at a heat not exceeding 130° F., the plant yields a rich violet-red colour. This is Hellot's test for the discovery of a colorific property in lichens [Berthollet On Dyeing, by Ure, vol. ii. p. 184; also, Proceedings of Comm. of Agricult. of Asiatic Society, April 8th, 1837.]. By adding a solution of hypochlorite of lime to an alcoholic tincture, or to an alkaline infusion of the lichen, a fugitive blood-red colour is produced.
Physiological Effects.—Mucilaginous, emollient, and demulcent.
Uses.—In the Mauritius it is employed in decoction to alleviate cough. In Europe it is only employed as a colorific agent.
The Elements of Materia Medica and Therapeutics, Vol. II, 3th American ed., was written by Jonathan Pereira in 1853.