Some of the most useful dyes and the least known are to be found among the Lichens. They seem to have been used among peasant dyers from remote ages, but apparently none of the great French dyers used them, nor are they mentioned in any of the old books on dyeing. The only Lichen dyes that are known generally among dyers are Orchil and Cudbear, and these are preparations of lichens, not the lichens themselves. They are still used in some quantity and are prepared rather elaborately. But a great many of the ordinary lichens yield very good and permanent dyes. The _Parmelia saxatilis_ and _Parmelia omphalodes_, are largely used in the Highlands and West Ireland, for dyeing brown of all shades. No mordant is needed, and the colours produced are the fastest known. "Crottle" is the general name for Lichens in Scotland. They are gathered off the rocks in July and August, dried in the sun, and used to dye wool, without any preparation. The crottle is put into the bath with a sufficient quantity of water, boiled up, allowed to cool, then boiled up with the wool until the shade required is got. This may take from one to three or four hours, as the dye is not rapidly taken up by the wool. Other dyers use it in the following way: A layer of crottle, a layer of wool, and so on until the bath is full; fill with cold water and bring to the boil, and boil till the colour is deep enough. The wool does not seem to be affected by keeping it in the dye a long time. A small quantity of acetic acid put with the Lichen is said to assist in exhausting the colour. The grey Lichen, _Ramalina scopulorum_ dyes a fine shade of yellow brown. It grows very plentifully on old stone walls, especially by the sea, and in damp woods, on trees, and on old rotten wood. Boil the Lichen up in sufficient water one day, and the next put in the wool, and boil up again till the right colour is got. If the wool is left in the dye for a day or more after boiling it absorbs more colour, and it does not hurt the wool but leaves it soft and silky to the touch, though apt to be uneven in colour. Some mordant the wool first with alum, but it does not seem to need it. The best known of the dye Lichens are _Parmelia saxatilis_ and _Parmelia omphalodes_ which are still largely used in Scotland and Ireland for dyeing wool for tweeds. The well-known Harris tweed smell is partly due to the use of this dye. Other Lichens also known for their dyeing properties are: _Parmelia caperata_, or Stone Crottle, which contains a yellow dye, _P. ceratophylla_, or Dark Crottle, and _P. parietina_, the common wall Lichen, which gives a colour similar to that of the Lichen itself, yellowish brown. A deep red colour can be got from the dull grey friable Lichen, common on old stone walls. The bright yellow Lichen, growing on rocks and walls, and old roofs, dyes a fine plum colour, if the wool is mordanted first with Bichromate of Potash.