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European authors ; and this conception is admirably expressed in 

 the Synopsis, where the species are grouped so as to show their 

 natural relations, and their multiplication is avoided as much as 

 possible. It would be an omission not to mention the names of his 

 collaborators in the collection of material for his work, Russell, 

 Oakes and Frost in New England, Hayden, Hall, Macoun and Bo- 

 lander for the Western region, Peters, Ravenel, Curtis and Austin 

 for the Southern States, and Charles Wright for Cuban and exotic 

 Lichens. All Lichens collected in this country went to him for final 

 determination, and without consulting his herbarium no one can 

 hope to become fully acquainted with our Lichens. A " Sylloge " 

 of all his scattered observations and descriptions would be a boon 

 to our Lichenists and a fitting monument to his fame. 



The present decade will perhaps come to be considered as closing 

 the sixth of Krempelhuber's Periods, and as inaugurating, with 

 Schwendener and Minks, a new and revolutionary one. Whether 

 the views of either of these prevail or not, it is time the discordance 

 that has prevailed for so long a time, the difference between leading 

 authorities as to the foundations of the system, and the basis of 

 genera and species should come to an end, and that harmony instead 

 of discord and confusion should prevail. Tuckerman's labors were 

 directed to that end ; and the American student can for the present 

 do no better than to accept him as a leader and guide. 



CHARTER IV. 



HELPS TO THE STUDY OF LICHENS. 



To the American student the Study of Lichens presents peculiar 

 diflaculties.' Some of these are (1) the want of any work containing 

 the descriptions of all known Lichens ; (2) the difficulty of procur- 

 ing the works upon Lichens, and the fact that they are mostly in 

 foreign languages, Latin, German, French, &c., and that many 

 useful works are published in the proceedings of learned societies, 

 and are not to be consulted here ; (3) the embarrassment arising 

 from the multiplicity of systems, and the differences of opinion as 

 to the limits of Genera and Species ; (4) the vast synonomy, which 

 renders it often difficult to decide as to the proper name of a plant ; 

 (5) the extent and variety of our own Lichen Flora, and the incomplete- 

 ness of the work of our great authority, Tuckerman. Such helps as 



