Dyer’s Orchella Weed.—This is one of the most valuable of the vegetable products of Eastern Africa, and may be found, in greater or less quantity, from the Cape of Good Hope to the Red Sea.
There are several species or varieties of this lichen; and it has been used, from the most ancient times, for the purpose of supplying a colouring matter.
Theophrastus, Dioscorides, and Pliny mention a plant which grew near the ground on the rocks of Crete, and was used for dying purple; the last named of these three ancient writers calls this plant phycos thalassion; while Dioscorides says that some persons imagine that the paint used by women was made from this plant; but he adds that it was a root bearing this name.
The phycos thalassion of the ancients has been usually assumed to be the Rocilla tinctoria; and Bory de St. Vincent even thinks that the ancients made their celebrated purple dye, brought from the isles of Elishah, with the R. tinctoria, which he therefore calls R. purpura antiquorum.
In the fourteenth century, a nobleman, named Ferro, or Fredrigo, of German extraction, while travelling in the Levant, discovered that the colour might be extracted from this plant by the action of urine: in the Levant, this plant was called respio or respo, and in Spain, orciglia. Proceeding to Florence, where his family were settled, he made known his discovery, and it was applied to the dyeing of wool. His family was ennobled for this discovery, under the name of Oricellarii, altered to Rucellai, and became greatly enriched in consequence of the monopoly of the importation of this weed, which they had for some generations. From the name Rucellai, the generic term Rocella is supposed to be derived.
All species and varieties of Rocella found in commerce bear the general appellation of Orchella weed; but they are distinguished by the name of the country from which they are exported.
The commercial kinds of Orchella weed may be conveniently arranged in two divisions.
1st. Orchella weeds having a cylindrical tapering thallus—Rocella tinctoria.
Found in the Canary Islands; Western Islands; Cape de Verde Islands; some parts of the coast of Barbary; South America, and the Cape of Good Hope.