PREFACE. 



When Part VI. of the Catalogue of Canadian plants was pub 

 lished in 1892, there was sufficient material at hand to allow of 

 the inclusion of the Lichens and Liverworts in that number, but 

 there were still such large tracts of country in which no botanical 

 work had been done that it seemed advisable to confine the scope 

 of that volume to the Musci. The present part contains all the 

 species of Lichens and Liverworts known to occur in Canada, 

 and an addendum to Part VI. in which our knowledge of Ameri- 

 can Mosses north of the United States is brought up to date. 



My collections of Hepaticae were commenced in 1862, and the 

 specimens were examined and my determinations verified by Mr. 

 C. F. Austin, who continued to work at them up to the time of 

 his death. There was then no one in America to whom I cared 

 to send difficult species for determination, but shortly afterwards 

 I made the acquaintance of Mr. C. M. Pearson, of Manchester, 

 England, who undertook to examine my material. Mr. Pearson's 

 work resulted in a pamphlet published in 1892, in which were 

 enumerated all the species known to occur in Greenland, Canada 

 and Alaska. The total number of species enumerated in the 

 region covered by Mr. Pearson's list was 165. 



For many years, difficult specimens were submitted to Prof. 

 Underwood, who assisted me in many ways in my studies of 

 Liverworts, and later Prof. A. W. Evans, New Haven, Conn., gave 

 me valuable assistance, so valuable that without his help this 

 section of the catalogue could not have been written at this time. 

 Besides naming all my later collections, he carefully examined 

 many doubtful specimens that had accumulated since the publica- 

 tion of Mr. Pearson's list, and I was thus enabled to give these 

 doubtful species their proper place in the series. 



During the lifetime of Prof. Tuckerman, all my collections of 

 Lichens were examined by him, and after his death Dr. Eckfeldt, 

 of Philadelphia, Pa., was of much assistance to jiie in my Lichen 

 studies. In 1895 I opened up a correspondence with Rev. J. S. 

 Deichmann Branth, of Sneptrup, Denmark, and by his kindness 

 and assistance I have been enabled to complete my list of the rock 

 Lichens, and those obscure forms grouped after Lecidea. 



