130 L1CHENES. 



first plants which clothe the bare rocks and form a humus for 

 others of a higher organization to live and flourish in. In the 

 arts, in domestic economy, (scarcely in medicine,) many of them 

 are highly valuable, as will be mentioned under the respective 

 species. 



The Genera of Acharius, being those in most general use, are 

 here adopted, with some modifications : and the arrangement 

 followed is founded on that of M. Fee (published in his 

 " Essai sur les Cryptogames des ecorces exotiques officinales"}, 

 which arrangement appears to me to be the most natural of 

 any that has hitherto appeared. Esch wetter, Fries, Agardh, 

 Meyer, Walroth, and Chevalier, have likewise proposed new 

 methods ; but I have not yet had the opportunity of studying 

 their respective merits. It will be seen in this and the remain- 

 ing Orders of Cryptogamia, that the plant itself, independent of 

 the fructification or reproductive organs, by whatever name they 

 may be called, is essential in distinguishing the genera, as is 

 also the fructification. 



It is to be regretted that no publication of specimens of the 

 Lichens of Great Britain, (which have been so successfully 

 ascertained and described by the labours of Dickson, Smith, 

 Turner, and Borrer) similar to those of 31osses by Drummond 

 and Hobson, and of Hepaticce by the latter, has appeared. 

 Such a work (including other Cryptogamic Plants,) was begun 

 by Mr. Baxter of Oxford, but the author died before it had 

 reached the 3d. Fasciculus ; and no one has undertaken the con- 

 tinuation. Upon the Continent many have appeared of consider- 

 able merit, and which have proved of great utility in the study of 

 Cryptogamic Botany. I may particularly mention the Stirpes 

 CryptogamiccB Vogeso-RJienance of Mougeot and Nestler, the 

 Cryptogamische Gewachse besonders des Fichtelberg of Funck, 

 the Lichenes Exsiccati of Reichenbach and Schubert, and above 

 all the Lichenes Helvetici Exsiccati of my valued .and learned 

 friend M. Schcerer, Minister of Lauperswyl, in the Canton of 

 Berne, with whom I have collected many of the specimens 

 contained in his work, in one of the most delightful excursions 

 I ever made upon the Alps of Switzerland. These publica- 

 tions, however, are rare in this country, and I shall limit my 

 references to that of M. Schserer, than whom no one has studied 

 the family with more ardour and enthusiasm, nor under more 

 favourable circumstances ; whether his situation be considered, 

 surrounded as is his place of residence by lofty mountains and 

 the noblest forests, or his extended correspondence with the 

 most eminent Lichenographists of Europe. With such helps 

 as these now enumerated, and such figures as those of English 

 Botany, the difficulty of studying this extensive and intricate 

 tribe will be found much diminished. 



