6. Lichenes erecti ramosi plani.
Such as consist of a firm tough matter, disposed into flat and thin ramifications growing erect, and bearing their scutellæ upon the edges, surfaces, and at the extremities.
This division comprehends the flat branched tree-mosses of authors; many of the fourth order of Haller’s lichens; the first part of the second division of series the second in Dillenius; and the platisma of Hill.
The plants of this division grow upon old trees, especially in thick and unfrequented woods; some of them upon rocks: they are many of them extremely common in England upon all kinds of trees. As they were some of the most obvious, so they were some of the first lichens noticed by the old writers, by whom they were called lichenes arborum.
The mosses of this order were substituted in the room of the usnea in the composition of the pulvis cyprius. The very species, which was most frequently used for this purpose, was the channel-leaved lichenoides of Dillenius[115], on account of its being easily reduced into a fine powder, of a good white colour. Nevertheless, others are undoubtedly as well adapted to the same purposes: and, if it was of importance enough to employ them to any purposes of the like nature in our own country, they might be procured in sufficient plenty.
One of the plants of this order is applicable to the same uses as the Canary-weed, and is reckoned not much inferior to it; and as it is found in the same places, it is very often packed up with it in considerable quantities. Dillenius calls it The flat dyers lichenoides with longer and sharper horns[116]. It is truly and properly a plant of the lichen genus, tho’ the older writers of the last century called it a fucus. They were led into this mistake by its having flat ramifications, and from its growing on the rocks by the sea side. It is found in the East Indies upon trees, and is frequent on the coasts of the Mediterranean, as well as about the Canary Islands.