_Some of them have a powdery appearance, and others are crustaceous, leaf-like, shrub-like, herbaceous, or gelatinous._ 282. _The CALCAREOUS LICHEN_ (Lichen calcareus) _consists of a white crust with black tubercles._ This plant, which is found on lime-stone rocks in Wales, and the north of England, is used in dyeing woollen and other cloths a scarlet colour. 283. _CRAB'S-EYE LICHEN_ (Lichen parellus) _is a crustaceous, whitish, and granulated vegetable substance, with cups of the same colour, which have a thick and blunt border._ From this lichen, which is found on rocks and stones in mountainous countries, and sometimes on stones near the sea-shore, is prepared the bluish pigment called _litmus_. It is chiefly collected from rocks in the north of England, packed in casks, and sent to London for sale. 284. _TARTAREOUS LICHEN_ (Lichen tartareus) _is a whitish, crustaceous, vegetable production, with yellow cups or shields, which have a whitish border._ The inhabitants of the Highlands of Scotland gather this species of lichen from the rocks, and, after cleaning, and some further preparation, which is kept a secret by the manufacturers, they form it into cakes. These, when dried, are pulverized, and sold to dyers by the name of _cudbear_, which is a corruption of Cuthbert, the name of its inventor. In conjunction with alum, the powder of the tartareous lichen is used in dyeing scarlet, and also for striking a purple dye; but the colour produced by it is not very permanent. 285. _ARCHELL, or PURPLE ROCK LICHEN_ (Lichen omphalodes), _is a vegetable production, of somewhat crustaceous consistence, and leaf-like form; the segments with many lobes, and of dark purplish brown colour, with dull purple saucers._ This kind of lichen grows upon rocks on the high stony moors of several parts of England, Wales, and Scotland. When properly prepared, it imparts to woollen cloth a reddish brown colour, or a dull but durable crimson. If wool that has been dyed with it be dipped into a blue vat, it will acquire a beautiful purple tinge. It is sometimes used as a styptic; and was formerly applied as a remedy in inflammatory fevers and other complaints; but, in the latter respect, it is now entirely neglected. 286. _ORCHALL, or DYER'S LICHEN_ (Lichen rocella), _is a somewhat crustaceous and shrub-like vegetable production, of nearly cylindrical form, solid, without leaves, but little branched, and with blackish brown alternate tubercles._