45 



Weber, Hagen, Ehrhart, Dickson, Villars, Swartz, Smith, and 

 Wulfen. And thus we arrive at the third epoch of disposition. 

 The need of more genera was generally felt, and a more accurate 

 analysis of the fructification which Hedwig began first to insti- 

 tute, proved their naturalness. Hill (1751 ) had, indeed, already, and 

 Adanson (1763) attempted the distinction of some few genera, but 

 of much higher import were the labors of Weber (1778), Willdenow, 

 and Humboldt, to this end. Hoffmann (1784) attempted a complete 

 reformation of the order, in several elegant but not thoroughly sci- 

 entific works, wherein he indicated incompletely some important 

 parts of our present system, and illustrated the species with figures. 

 Schreber, also, about this time attempted a distribution of lichens 

 in sixteen subgenera. But PERSOON and SCHRADER are the 

 founders of our present views of the science generally, the first 

 establishing important genera, and the second proposing general 

 principles of disposition from the fructification, which have now 

 revived. ACHARIUS and FLOERKE followed, the first devoted to 

 the description and arrangement of species, the last to their careful 

 study in nature. Wahlenberg elegantly described and disposed 

 the lichens of Lapland, avoiding many of the common errors of the 

 time. Turner observed carefully the British species, and, with 

 BORRER, illustrated all the more difficult genera, in descriptions 

 which have not been surpassed. Luyken collected with assiduity a 

 view of all that was known generally of the science. Decandolle 



S'oposed a new but not altogether successful disposition. Ramond, 

 ufour, Sommerfelt, Delise, Fee, greatly increased the number of 

 species. At length the observations of Fries and Scheerer, and the 

 analyses of Eschweiler brought in that reformation of the system 

 which WALLROTH and MEYER accomplished. The whole has 

 finally been comprehended, and, both in generals and particulars, 

 systematically disposed in the consummate work of FRIES. 



Auct. de Lichenologis: Fries, Lichenogr. p. 115; Luyken, Diss. 

 1. c. 



VIII. APHORISMI. 



1. Species unica in naturafixe circumscripta idea. Fr. Syst. Myc. 



2. Constat omne plantarum genus (et species) habere quod sit 

 cujusque suum; quod quid sit, nisi continua contemplatione rimeris 

 et extrices, nunquam adsequeris. Koch. Sal. 



3. Tantum e re variis rationibus considerata plena nascitur cog- 

 nitis. Verum et pulchrum sub variis fortnis manifestatur. Q,ui se 

 unicum et summum justum in generalibus plene amplexum esse 

 fingit, se et alios fallit. Fr. 



4. Externa facies inter Lichenes fallacissima est. Fr. 



5. Affinia non identica, et equidem lubentius distinguo simillima, 

 in natura diversam evolutionis seriem servantia, quam dissimillia, 

 sed ex eadem evolutionis serie facile confluentia. Ingenue fateor 

 Lichenum formas, ut externa facie maxime differant, ita maxime 

 mihi esse suspectas. Fr. 



6. Pra3cipue cavendurn ne ex apparentibus approximationibus 

 speciminum atypicorum diversa confundamus. Ad transitus de- 

 monstrandos seligi possunt specimina omnium Cladoniarum, Biato- 



