Philosophical transactions, Vol. L. Part II. For the year 1758. / Giving some account of the present undertakings, studies, and labours, of the ingenious, in many considerable parts of the world.

by Various; Royal Society

4. Lichenes crustacei.

Such as consist of a dry and friable matter, more or less thick, formed into flat crusts, very closely adhering to whatever they grow upon.

Some of the species of this division consist of an exceeding fine thin crustaceous, or rather, as Micheli calls it, farinaceous matter, the fructifications appearing in the form of tubercles. Others consist of a thicker scabrous crust, having the fructifications in the form of little cups, called scutellæ.

This division contains the first order of the lichenoides of Dillenius; the 5th, 6th, and 7th orders of Haller’s lichens; the lichenes leprosi and crustacei of Linnæus; and several of the placodium of Hill.

The species are numerous, and most of them very common on rocks, stones, old walls, the bark of trees, old pales, &c. which are commonly covered over with them, in undisturbed places. They form a very agreeable variety, and some of them have a very elegant appearance.

Dr. Dillenius describes a species of this order, which he found upon the tops of the mountains in Caernarvonshire in Wales; and which the inhabitants told him they used as a red dye, and found it preferable to the cork, or arcel, which they call kenkerig. He has intitled it, in English, The white tartareous scarlet-dying lichenoides[98]. He is of opinion, that this is the moss which Martin mentions, in his account of the Western Islands of Scotland, under the name of corkir; with which the inhabitants of the island of Sky dye a scarlet colour. They prepare it by drying, powdering it, and then steeping it for three weeks in urine. Linnæus queries whether this moss be not the same as his lichen calcareus[99]; a species so peculiar to limestone rocks, that where-ever that stone occurs among others, it may be distinguished at the first view by this moss growing upon it. This is a singularity which Dr. Dillenius has not mentioned in his moss: on the other hand, Linnæus does not mention any tinging property in his.

The pérèlle d’Auvergne, or orseille de terre, of the French, belongs to this order of lichens, and is called by Dillenius[100] The crayfish-eye-like lichenoides. It is gathered in large quantities in the province of Auvergne, and is used as orchel; to which however it is greatly inferior. They prepare it with lime and urine; and were acquainted with its use as a dye long before the Canary weed was known[101] to them; and it is at this day in more common use than the orchel. We have it frequent with us upon old walls, rocks, and stones; but it is to be had in larger quantities in several other parts of Europe.

The mealy tartareous lichenoides[102] with brown dishes, forms an article of trade with the people of West Gothland. They manufacture a beautiful red dye from it, which they sell under the name of byttelet[103]. Dr. Hill says we have this moss abundantly in Leicestershire and Warwickshire.

The Welch make a red dye, with urine, from another moss of this order, which Dillenius describes[104] by the name of The large leprous lichenoides with yellow plates. These are not the only species, which are endowed with a tinging quality: other kinds have been observed to give a red or purple colour to paper in which they have occasionally been inclosed. Doubtless several would, upon sufficient trials, be found to answer equally well with the orchel.

With regard to these crustaceous mosses in general, it is highly worthy our regard, that in the œconomy of nature they answer singular and important uses. To an unobserving eye, no class of vegetables may appear more insignificant, or less adapted to advantageous purposes in the creation, than these. This vulgar estimation of things is frequently erroneous; and it is certainly so in the instance before us. These minute and seemingly insignificant mosses serve, under some circumstances, to valuable purposes. No sooner is a rock left bare by the sea, but these lichens lay the foundation for its future fertility. Their seeds, which are presently brought thither by the winds, soon cover it all over. These corrupting, presently afford a soil sufficient to nourish other smaller mosses; which, in their turn, form one deep enough for larger plants and trees; and thus the rock becomes a fertile island[105].