VI BULLETIN OP THE TJNIVEBSITY OF WISCONSIN. 



SCOPE OP THE KEYS. 



In the keys we have endeavored to include all the species 

 reported or described as belonging to our flora, unless a 

 later special study of the genus has shown the addition to 

 be untenable. Such special studies are cited in the keys. 

 The incompleteness of many descriptions, and the lack of 

 diagnostic characters have seriously hampered us in re- 

 arranging the keys, and they will fail, therefore, in many 

 cases to differentiate described species. We have been at 

 considerable pains to include as many of the barren and 

 insufficiently described species as possible, in order that 

 these may be recognized, if they exist, or may be referred 

 to their appropriate place. Material which will enable 

 students either to diagnose them clearly or to overthrow 

 them would be of great value. 



The keys do not generally discriminate varieties, but it 

 is very important that collectors and amateurs keep in 

 mind the variability of the mosses and seek to bring to 

 light as many facts as possible bearing on this problem, so 

 that the range of variability may be ascertained. To facil- 

 itate this we have also collected descriptions of varieties 

 not appearing in the Manual. In these varietal descrip- 

 tions the comparisons, unless otherwise stated, are with 

 the characters of the species. 



NOMENCLATURE. 



It seemed to us highly desirable to avoid the making of 

 new names in a compilation like this. We have therefore 

 used, as a basis for our work, Renauld and Cardot's Musci 

 Americce Septentrionalis.' In basing our keys upon that list 

 we do not thereby express our adherence to the nomencla- 

 ture employed. Of many species therein neither the 



' Published in the Revue Bryologique 19: 65-69. 1892 and 20: 1-32. 

 1893. Afterward this was issued as a separate and, most unfortunately, 

 e-paged and revised. 



