PREFACE. V 



de Terre-JVeuve, and the specimens of those collected by him, 

 Mr. Despreaux, and others, preserved in the Royal Herbarium 

 at Berlin, in that of Professor Kunth, and in those of the late 

 Baron Delessert and of Dr. Montagne, at Paris. To the vast 

 herbarium of Sir W. J. Hooker I am indebted, not only for 

 numerous Lichens of Canada and Newfoundland, but for a large 

 collection of the arctic species obtained in the different voyages 

 of Parry, Franklin, and others ; and to these, and his various 

 Enumerations, together with those of Mr. Brown, Sir John Rich- 

 ardson, and Dr. Greville, I owe most of the arctic citations. 

 The late venerable Mr. Menzies also favoured me with a nearly 

 entire set of the Lichens collected by him on the Northwest 

 Coast of America. 



The genera separated from Lichenes by Fries, and referred to 

 his family Byssacece, have not yet been fully studied in this coun- 

 try ; but these plants are so closely related to Lichenes, that I 

 have enumerated our ascertained species, as an appendix, at 

 the end. 



The present occasion does not permit me to offer more than 

 general acknowledgments to the eminent botanists whose kind 

 consideration has encouraged the progress of this work. But I 

 cannot conclude it without expressing my indebtedness to the 

 great kindness and liberality of Sir W. J. Hooker, and of Wil- 

 liam Borrer, Esq., the learned lichenographer of Britain ; to my 

 much respected friend, Dr. Klotzsch of Berlin, without whose 

 liberal assistance in the study of the Floerkean herbarium it could 

 not have been undertaken ; and to my esteemed friend Dr. Gray, 

 at whose instance it has been prepared. 



Cambridge, i/h February, 1848. 



