-89- 



EXPLANATION OF PlATES VIII-IX 



Plate VIII 



1. The dubious Linnean type of Ramalina calicaris at London. (Nat. size.) 



2. One of the determinable Linnean types of Ramalina calicaris at London. 



3. The Retzius type of Lichen scopulorum at Lund. (Nat. size.) 



4. Acharian authentic material of Ramalina scopulorum var. c. cuspidata 

 at London. (Slightly reduced.) 



5. The Nylander type of Ramalina evernioides at Paris. (Nat. size.) 



Plate IX 



1. The Acharian types of Parmelia polymorpha and the va.neties flabellulata, 

 strepsilis, tinctoria, capitaia, ligulata, and emplecta at Helsingfors. (Nat. size.) 



2. The Acharian types of Ramalina pollinaria and the varieties elatior and 

 humilis at Helsingfors. (Nat. size.) 



NORTH AMERICAN FLORA, Vol. 15, Parts 1 and 2 



Sphagnaceae — Leucobryaceae. 



Every student of North American Mosses has looked forward with eagerness 

 to the appearance of Volume 15, and the two parts already issued will receive 

 a warm welcome. 



Part I includes the Sphagnaceae by Albert LeRoy Andrews, the Andreaea- 

 ■ceae by EHzabeth Gertrude Britton and Julia Titus Emerson, also the Archidi- 

 aceae, Bruchiaceae, Ditrichaceae, Bryoxiphiaceae, Seligeriaceae, by Mrs. Britton. 

 Part 2, Dicranaceae, Leucobryaceae, by Robert Statham Williams. 



The style and arrangement, the exclusiveness and inclusiveness are in keep- 

 ing with the other parts already pubhshed. No work on North American mosses 

 has ever been so inclusive or complete, as the range includes all the Americas 

 except South America and adjacent islands. 



The arrangement of families and genera in the main follows Engler and 

 Prantl, but the subfamilies of the Dicranaceae are in many cases raised to family 

 rank, a procedure that is of questionable desirability. 



The conservative attitude shown in the matter of creating new species will 

 meet with general approval we feel sure. The number of new species is very 

 few — seven were all that were noted — and these were from the little explored 

 regions of the range. 



Linnaeus, 1753, is taken as the starting point of binomial nomenclature 

 in mosses as in flowering plants and there are no startling innovations in nomen- 

 clature. Most of the names used that differ from those in our earlier literature 

 have become fairly familiar to those who have used recent publications on North 

 American mosses. 



