X PREFACE 



generic character that is recognizable in the field with- 

 out the aid of a lens. In the descriptions of a few gen- 

 era some additional characteristics visible with a hand- 

 lens are given. These are not necessar}^ for the use of 

 the Keys, but are of interest in bringing out some 

 special points. 



In arranging the Keys it seemed best not to carry 

 them out under many headings to a single genus, but 

 to keep them as simple as possible and group even 

 several genera under one head. This plan requires the 

 student to refer constantly to the illustrations and 

 descriptions and in this way to become familiar with 

 the names and appearances of the different mosses. 



The Keys have been tested satisfactorily by several 

 people. When they did not work out correctly, it was 

 usually found that the trouble lay in failure either to 

 read the explanatory chapters, to follow the Keys care- 

 fully, or to study the descriptions thoroughly. 



The mosses included in the Keys are those that are 

 commonly or occasionally collected in the northeastern 

 part of the United States. But the Keys really cover a 

 much larger field, many of the mosses being widely 

 distributed, as will be seen by reading the range given 

 with each genus or species. 



Four full pages of illustrations of terms used in de- 

 scribing mosses accompany the chapters on ''Habit 

 and Manner of Growth," "Leaves," and ''Capsules." 

 Other illustrations occurring throughout the text, with 

 the exception of a few in the Introduction, are drawn 



