IV 



families, and genera, these authors have been followed closely, 

 and, while there is much to be said against their arrangement 

 of families in certain cases, it is nevertheless verj- probable that 

 their work will remain for a long time the standard and that, 

 from the standpoint of convenience at least, a similar sequence 

 of families in this Manual is justified. In the determination of 

 the various species the author has, naturally, had recourse to 

 the various works of Sullivant, Lesquereux & James, Barnes 

 & Heald, Grout, and others among the American bryologists, 

 and, among the European bryologists, particularly Dixon and 

 Jameson. In the determination of the Sphagnums the works 

 of Warnstorf, Roth, and Braithwaite were found particularly 

 useful, while in the treatment of synonymy the main reliance 

 has been placed on the Index Bryologictts of E. G. Paris. 



In nomenclature the rulings of the International Botanical 

 Congress, held in Brussels in 1910, have been followed, taking 

 as the starting point the Species Muscorum of Hedwig (1801) 

 and the three subsequent "Supplements" by Schwaegrichen, 

 Hedwig's having been the first comprehensive work to deal 

 with the mosses in a modern way. In the present Manual the 

 principle of priority has been followed without exception, dat- 

 ing from Hedwig, and a few new combinations have been 

 found necessary. Plant names which have been adopted from 

 pre-Hedwigian sources without important changes in nature or 

 in status are indicated by a double citation of authors, the 

 pre-Hedwigian author being cited first, followed by a comma, 

 and then the name of Hedwig or Schwaegrichen or of the 

 post-Hedwigian author, as the case may be. In case the name 

 of the plant has been derived from pre-Hedwigian sources, but 

 has been used in a different rank or, in the case of species, has 

 been transferred from one genus to another, the name of the 

 pre-Hedwigian author has been enclosed in square brackets. 



So far as it has been possible to do so the descriptions of 

 the various species have been drawn up from specimens col- 

 lected in the region covered by the Manual. Where speci- 

 mens of species reported as occurring in the region or thought 

 likely to be eventually discovered in the region have not been 

 available for description, the description has been in part com- 

 piled and in part drawn up from specimens from other regions. 

 It has been the aim to represent by original drawings, com- 

 pletely and in considerable detail every species of which speci- 

 mens collected in the region of the Manual have been available. 

 In the list of specimens, which, in the Manual, follows the 

 description of each species, the particular specimen figured has 

 been so indicated and the fact that the specimen has been thus 

 figured has been recorded on the pocket containing the speci- 

 men in the Herbarium of the Carnegie Museum. All drawings 



