M. Vaillant, in the _Botanicon Parisiense_, retains Tournefort’s names. Many of these lichens, as well as other mosses, are accurately represented in the elegant tables, which adorn that work. Dr. Haller tells us he learnt to distinguish almost all the mosses solely by the help of these tables, so well are they expressed. The lovers of botanic science are greatly indebted to Boerhaave for his publication of that work. Micheli, after Tournefort, adopts the term _lichen_, and comprehends all the species under it, except one or two, which he calls _lichenoides_. This author however does not take into this genus the liverwort of the _materia medica_; he describes the species of that genus under the name of _marchantiæ_. Near twenty of the plates in his _Nova Plantarum Genera_ are taken up in representing various species of this genus. In this work they are divided into thirty-eight orders or subdivisions; a circumstance very necessary indeed, considering how greatly he has multiplied the number of the species. It is to be regretted, that so indefatigable an author, one whose genius particularly led him to scrutinize the minuter subjects of the science, should have been so solicitous to increase the number of species under all his genera: an error this, which tends to great confusion and embarassment, and must retard the progress and real improvement of the botanic science. Dr. Haller retains Micheli’s term, and enumerates 160 kinds in his _Enumeratio Stirpium Helvetiæ_: he divides them into seven orders, according to the following titles: 1. _Lichenes corniculati & pixidati._ 2. _Lichenes coralloidei._ 3. _Lichenes fruticosi alii._ 4. _Lichenes pulmonarii._ 5. _Lichenes crustacei scutis floralibus ornati._ 6. _Lichenes scutellis ornati._ 7. _Lichenes crustacei non scutati._ The extensive number of the species, and the difficulty of distinguishing them with a tolerable degree of certainty, has deterred Dr. Haller from adding so full and complete a list of synonyms to the plants of this genus as he has elsewhere done in that splendid work. Plate the 2d exhibits several elegant sorts of these lichens. Linnæus, and the followers of his method, who seem to have established their generical character from Micheli’s discoveries, retain also his generical title. Micheli’s passion for the multiplication of species is no-where more conspicuous than in the plants of this genus, which he has most enormously augmented to the number of 298 species. The Swedish professor cannot be charged with this foible: it is one of the excellencies of his writings, that they inculcate the reverse. He has so far retrenched this genus, that in his general enumeration of plants he recounts only eighty species belonging to it. They are in this work divided into eight orders, according to the difference of appearance which they form by their _facies externa_, little or no regard being had to what are usually called the parts of fructification.