So far as the parts of fructification are distinguishable in these plants, they appear in different forms upon different species: on some, in the form of tubercles; on others, in the form of little concave dishes, called _scutellæ_; on others, of oblong flat shields or pelts. All these are conceived by Micheli and Linnæus to be receptacles of male flowers. The female flowers and seeds are suspected by the same authors to be dispersed in the form of farina or dust upon the same plants, and in some instances on separate ones. Dillenius has not dared to determine any thing positively with regard to the real parts of fructification in these lichens: time will hereafter, it is to be hoped, throw more light upon the subject. In order to convey a more distinct idea of the several plants of this genus, which enter into œconomical or medical uses in the various parts of the world, we shall distribute them into several orders, according to the custom of former writers: and as is not consistent with our plan to describe each of these species, we shall refer to the page of the more modern authors, where they may be found. 1. Lichenes filamentosi. _Such as consist of mere solid filaments, of a firm and solid but flexible texture, having the appearance of fructification in the form of_ scutellæ, _or flat round bodies growing from the sides or extremities of these filaments_. This order or division comprehends the hairy tree-mosses, or _usnea_ of Dillenius and Hill; several of the species of the fifth order of lichens of Micheli; and the _lichenes filamentosi_ of Linnæus. Dr. Dillenius describes sixteen species under the term _usnea_, several of which are found in England, tho’ some of them, as the common _usnea_ of the shops, but very sparingly, and none of them in any considerable plenty. The thick woods in many other parts of Europe, and the rest of the globe, afford them in great plenty. They hang from the branches of various kinds of trees, like large tufts of hair, to a considerable length: some species grow several feet long. The rocks on the tops of high mountains afford several kinds. They are of various colours; some whitish, ash-coloured, others grey or blackish, and two or three species have a yellow or orange hue.