vi PREFACE. 



characters to be more simply diagnostic. In monotypic genera, it has 

 been found more convenient to give the details under the species, in 

 the form of a specific character. Throughout the work, from the order 

 down to the species or variety, the endeavor is to avoid repetition of 

 statement. 



The names of introduced species, sufficiently established to claim a 

 place in our flora, are printed in small capitals, as are such adventitious 

 or extraneous species as require mention. 



In the accentuation of generic, sectional, and specific names, no 

 attempt is made (as in the Manual of Botfany of the Northern United 

 States and other works) to mark the quality of the accented vowel, but 

 only to designate the syllable upon which the principal accent falls. 



Compactness being essential, only the leading synonymy and most 

 important references are given, and these briefly. All deficiency in this 

 respQct will be amply supplied by the Bibliographical Index to North 

 American Botany, pre'pared at the Harvard University Herbarium 

 by Sereno Watson, and now in course of publication by the Smith- 

 sonian Institution. The first part of this most important adjunct to the 

 present work, which is just issued, gives the full bibliography of the 

 Polypetal^ (the subject of the first volume of Torrey and Gray's Flora 

 of North America, published in 1838 and 1840), with revision, critical 

 corrections, and additions up to the present time. Its continuation may 

 be expected to proceed pari passu with this Flora. 



Harvard Uxiversity Herbarium, 



Cambridge, Massachusetts, April 10, 1878. 



