250 PHILOSOPHICAL TRANSACTIONS. [aNNO 1758. 



The genus of lichenoides contains 1 35 species, disposed according to the fol- 

 lowing scheme: 



, „ ^ r 1 . Tuberculosae. 8. 



Ordol. Species aphyllae mere crustaceae. | 2. Scutellat^. 18. 



f 1. Grelatinosae tuberculosae et scutellatae. 35. 

 Ordo 2. Species foliosae. \ 2. Aridiores et e^isuccae, scutellatae. 100. 



t 3. Aridiores peltatae et clypeatae. 121. 

 These plants are not only largely described, and accompanied with the most per- 

 fect assemblage of s}TK)nyms, but every species is accurately figured, and many 

 of them in various views, and at different ages of their growth ; by which this 

 laborious work, notwithstanding it is conversant on the minutest, and conse- 

 quently the most abstruse parts of botany, may yet be justly esteemed, 

 without any exaggeration, one of the most complete works extant of the kind. 



Dr. Hill, in his History of Plants, has disposed them into 5 genera, under the 

 following names : 1 . Usnea, comprehending the hairy tree-mosses ; 2. Platysma, 

 flat-branched tree-mosses, the lungwort, and others; 3. Cladonia, containing 

 the orchel and coralline-mosses; 4. Pyxidium, the cup-mosses ; 5. Placodium, 

 the crustaceous mosses. The plants of this extensive genus are very different in 

 their form, manner of growing, and general appearance : on which account 

 those authors who preserve them under the same name, saw the propriety an<J 

 necessity of arranging them into different orders and subdivisions, that the species 

 might be distinguished with greater facility. On the same principle Dr. Dil- 

 lenius and Dr. Hill have formed them into several genera. 



So far as the parts of fructification are distinguished in these plants, they aj)- 

 pear in different forms on different species ; on some, in the form of tubercles ; 

 on others, in the form of little concave dishes, called scutellae ; on others, of 

 oblong flat shields or pelts. All these are conceived by Micheli and Linneus 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 on the same plants, 

 and in some instances on separate ones. Dillenius has not dared to determine 

 any thing positive with regard to the real parts of fructification in these lichens : 

 time will hereafter, it is to be hoped, throw more light on the subject. 



In order to convey a more distinct idea of the several plants of this genus, 

 which enter into economical 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 it 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 tex- 



